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Study Overview
Objective. To compare the effects of intermittent energy restriction (IER) with those of continuous energy restriction (CER) on blood pressure control and weight loss in overweight and obese patients with hypertension during a 6-month period.
Design. Randomized controlled trial.
Settings and participants. The trial was conducted at the Affiliated Hospital of Jiaxing University from June 1, 2020, to April 30, 2021. Chinese adults were recruited using advertisements and flyers posted in the hospital and local communities. Prior to participation in study activities, all participants gave informed consent prior to recruitment and were provided compensation in the form of a $38 voucher at 3 and 6 months for their time for participating in the study.
The main inclusion criteria were patients between the ages of 18 and 70 years, hypertension, and body mass index (BMI) ranging from 24 to 40 kg/m2. The exclusion criteria were systolic blood pressure (SBP) ≥ 180 mmHg or diastolic blood pressure (DBP) ≥ 120 mmHg, type 1 or 2 diabetes with a history of severe hypoglycemic episodes, pregnancy or breastfeeding, usage of glucagon-like peptide 1 receptor agonists, weight loss > 5 kg within the past 3 months or previous weight loss surgery, and inability to adhere to the dietary protocol.
Of the 294 participants screened for eligibility, 205 were randomized in a 1:1 ratio to the IER group (n = 102) or the CER group (n = 103), stratified by sex and BMI (as overweight or obese). All participants were required to have a stable medication regimen and weight in the 3 months prior to enrollment and not to use weight-loss drugs or vitamin supplements for the duration of the study. Researchers and participants were not blinded to the study group assignment.
Interventions. Participants randomly assigned to the IER group followed a 5:2 eating pattern: a very-low-energy diet of 500-600 kcal for 2 days of the week along with their usual diet for the other 5 days. The 2 days of calorie restriction could be consecutive or nonconsecutive, with a minimum of 0.8 g supplemental protein per kg of body weight per day, in accordance with the 2016 Dietary Guidelines for Chinese Residents. The CER group was advised to consume 1000 kcal/day for women and 1200 kcal/day for men on a 7-day energy restriction. That is, they were prescribed a daily 25% restriction based on the general principles of a Mediterranean-type diet (30% fat, 45-50% carbohydrate, and 20-25% protein).
Both groups received dietary education from a qualified dietitian and were recommended to maintain their current daily activity levels throughout the trial. Written dietary information brochures with portion advice and sample meal plans were provided to improve compliance in each group. All participants received a digital cooking scale to weigh foods to ensure accuracy of intake and were required to keep a food diary while following the recommended recipe on 2 days/week during calorie restriction to help with adherence. No food was provided. All participants were followed up by regular outpatient visits to both cardiologists and dietitians once a month. Diet checklists, activity schedules, and weight were reviewed to assess compliance with dietary advice at each visit.
Of note, participants were encouraged to measure and record their BP twice daily, and if 2 consecutive BP readings were < 110/70 mmHg and/or accompanied by hypotensive episodes with symptoms (dizziness, nausea, headache, and fatigue), they were asked to contact the investigators directly. Antihypertensive medication changes were then made in consultation with cardiologists. In addition, a medication management protocol (ie, doses of antidiabetic medications, including insulin and sulfonylurea) was designed to avoid hypoglycemia. Medication could be reduced in the CER group based on the basal dose at the endocrinologist’s discretion. In the IER group, insulin and sulfonylureas were discontinued on calorie restriction days only, and long-acting insulin was discontinued the night before the IER day. Insulin was not to be resumed until a full day’s caloric intake was achieved.
Measures and analysis. The primary outcomes of this study were changes in BP and weight (measured using an automatic digital sphygmomanometer and an electronic scale), and the secondary outcomes were changes in body composition (assessed by dual-energy x-ray absorptiometry scanning), as well as glycosylated hemoglobin A1c (HbA1c) levels and blood lipids after 6 months. All outcome measures were recorded at baseline and at each monthly visit. Incidence rates of hypoglycemia were based on blood glucose (defined as blood glucose < 70 mg/dL) and/or symptomatic hypoglycemia (symptoms of sweating, paleness, dizziness, and confusion). Two cardiologists who were blind to the patients’ diet condition measured and recorded all pertinent clinical parameters and adjudicated serious adverse events.
Data were compared using independent-samples t-tests or the Mann–Whitney U test for continuous variables, and Pearson’s χ2 test or Fisher’s exact test for categorial variables as appropriate. Repeated-measures ANOVA via a linear mixed model was employed to test the effects of diet, time, and their interaction. In subgroup analyses, differential effects of the intervention on the primary outcomes were evaluated with respect to patients’ level of education, domicile, and sex based on the statistical significance of the interaction term for the subgroup of interest in the multivariate model. Analyses were performed based on completers and on an intention-to-treat principle.
Main results. Among the 205 randomized participants, 118 were women and 87 were men; mean (SD) age was 50.5 (8.8) years; mean (SD) BMI was 28.7 (2.6); mean (SD) SBP was 143 (10) mmHg; and mean (SD) DBP was 91 (9) mmHg. At the end of the 6-month intervention, 173 (84.4%) completed the study (IER group: n = 88; CER group: n = 85). Both groups had similar dropout rates at 6 months (IER group: 14 participants [13.7%]; CER group: 18 participants [17.5%]; P = .83) and were well matched for baseline characteristics except for triglyceride levels.
In the completers analysis, both groups experienced significant reductions in weight (mean [SEM]), but there was no difference between treatment groups (−7.2 [0.6] kg in the IER group vs −7.1 [0.6] kg in the CER group; diet by time P = .72). Similarly, the change in SBP and DBP achieved was statistically significant over time, but there was also no difference between the dietary interventions (−8 [0.7] mmHg in the IER group vs −8 [0.6] mmHg in the CER group, diet by time P = .68; −6 [0.6] mmHg in the IER group vs −6 [0.5] mmHg in the CER group, diet by time P = .53]. Subgroup analyses of the association of the intervention with weight, SBP and DBP by sex, education, and domicile showed no significant between-group differences.
All measures of body composition decreased significantly at 6 months with both groups experiencing comparable reductions in total fat mass (−5.5 [0.6] kg in the IER group vs −4.8 [0.5] kg in the CER group, diet by time P = .08) and android fat mass (−1.1 [0.2] kg in the IER group vs −0.8 [0.2] kg in the CER group, diet by time P = .16). Of note, participants in the CER group lost significantly more total fat-free mass than did participants in the IER group (mean [SEM], −2.3 [0.2] kg vs −1.7 [0.2] kg; P = .03], and there was a trend toward a greater change in total fat mass in the IER group (P = .08). The secondary outcome of mean (SEM) HbA1c (−0.2% [0.1%]) and blood lipid levels (triglyceride level, −1.0 [0.3] mmol/L; total cholesterol level, −0.9 [0.2] mmol/L; low-density lipoprotein cholesterol level, −0.9 [0.2 mmol/L; high-density lipoprotein cholesterol level, 0.7 [0.3] mmol/L] improved with weight loss (P < .05), with no differences between groups (diet by time P > .05).
The intention-to-treat analysis demonstrated that IER and CER are equally effective for weight loss and blood pressure control: both groups experienced significant reductions in weight, SBP, and DBP, but with no difference between treatment groups – mean (SEM) weight change with IER was −7.0 (0.6) kg vs −6.8 (0.6) kg with CER; the mean (SEM) SBP with IER was −7 (0.7) mmHg vs −7 (0.6) mmHg with CER; and the mean (SEM) DBP with IER was −6 (0.5) mmHg vs −5 (0.5) mmHg with CER, (diet by time P = .62, .39, and .41, respectively). There were favorable improvements in
Conclusion. A 2-day severe energy restriction with 5 days of habitual eating compared to 7 days of CER provides an acceptable alternative for BP control and weight loss in overweight and obese individuals with hypertension after 6 months. IER may offer a useful alternative strategy for this population, who find continuous weight-loss diets too difficult to maintain.
Commentary
Globally, obesity represents a major health challenge as it substantially increases the risk of diseases such as hypertension, type 2 diabetes, and coronary heart disease.1 Lifestyle modifications, including weight loss and increased physical activity, are recommended in major guidelines as a first-step intervention in the treatment of hypertensive patients.2 However, lifestyle and behavioral interventions aimed at reducing calorie intake through low-calorie dieting is challenging as it is dependent on individual motivation and adherence to a strict, continuous protocol. Further, CER strategies have limited effectiveness because complex and persistent hormonal, metabolic, and neurochemical adaptations defend against weight loss and promote weight regain.3-4 IER has drawn attention in the popular media as an alternative to CER due to its feasibility and even potential for higher rates of compliance.5
This study adds to the literature as it is the first randomized controlled trial (to the knowledge of the authors at the time of publication) to explore 2 forms of energy restriction – CER and IER – and their impact on weight loss, BP, body composition, HbA1c, and blood lipid levels in overweight and obese patients with high blood pressure. Results from this study showed that IER is as effective as, but not superior to, CER (in terms of the outcomes measures assessed). Specifically, findings highlighted that the 5:2 diet is an effective strategy and noninferior to that of daily calorie restriction for BP and weight control. In addition, both weight loss and BP reduction were greater in a subgroup of obese compared with overweight participants, which indicates that obese populations may benefit more from energy restriction. As the authors highlight, this study both aligns with and expands on current related literature.
This study has both strengths and limitations, especially with regard to the design and data analysis strategy. A key strength is the randomized controlled trial design which enables increased internal validity and decreases several sources of bias, including selection bias and confounding. In addition, it was also designed as a pragmatic trial, with the protocol reflecting efforts to replicate the real-world environment by not supplying meal replacements or food. Notably, only 9 patients could not comply with the protocol, indicating that acceptability of the diet protocol was high. However, as this was only a 6-month long study, further studies are needed to determine whether a 5:2 diet is sustainable (and effective) in the long-term compared with CER, which the authors highlight. The study was also adequately powered to detect clinically meaningful differences in weight loss and SBP, and appropriate analyses were performed on both the basis of completers and on an intention-to-treat principle. However, further studies are needed that are adequately powered to also detect clinically meaningful differences in the other measures, ie, body composition, HbA1c, and blood lipid levels. Importantly, generalizability of findings from this study is limited as the study population comprises only Chinese adults, predominately middle-aged, overweight, and had mildly to moderately elevated SBP and DBP, and excluded diabetic patients. Thus, findings are not necessarily applicable to individuals with highly elevated blood pressure or poorly controlled diabetes.
Applications for Clinical Practice
Results of this study demonstrated that IER is an effective alternative diet strategy for weight loss and blood pressure control in overweight and obese patients with hypertension and is comparable to CER. This is relevant for clinical practice as IER may be easier to maintain in this population compared to continuous weight-loss diets. Importantly, both types of calorie restriction require clinical oversight as medication changes and periodic monitoring of hypotensive and hypoglycemic episodes are needed. Clinicians should consider what is feasible and sustainable for their patients when recommending intermittent energy restriction.
Financial disclosures: None.
1. Blüher M. Obesity: global epidemiology and pathogenesis. Nat Rev Endocrinol. 2019;15(5):288-298. doi:10.1038/s41574-019-0176-8
2. Unger T, Borghi C, Charchar F, et al. 2020 International Society of Hypertension Global hypertension practice guidelines. J Hypertens. 2020;38(6):982-1004. doi:10.1097/HJH.0000000000002453
3. Müller MJ, Enderle J, Bosy-Westphal A. Changes in Energy Expenditure with Weight Gain and Weight Loss in Humans. Curr Obes Rep. 2016;5(4):413-423. doi:10.1007/s13679-016-0237-4
4. Sainsbury A, Wood RE, Seimon RV, et al. Rationale for novel intermittent dieting strategies to attenuate adaptive responses to energy restriction. Obes Rev. 2018;19 Suppl 1:47–60. doi:10.1111/obr.12787
5. Davis CS, Clarke RE, Coulter SN, et al. Intermittent energy restriction and weight loss: a systematic review. Eur J Clin Nutr. 2016;70(3):292-299. doi:10.1038/ejcn.2015.195
Study Overview
Objective. To compare the effects of intermittent energy restriction (IER) with those of continuous energy restriction (CER) on blood pressure control and weight loss in overweight and obese patients with hypertension during a 6-month period.
Design. Randomized controlled trial.
Settings and participants. The trial was conducted at the Affiliated Hospital of Jiaxing University from June 1, 2020, to April 30, 2021. Chinese adults were recruited using advertisements and flyers posted in the hospital and local communities. Prior to participation in study activities, all participants gave informed consent prior to recruitment and were provided compensation in the form of a $38 voucher at 3 and 6 months for their time for participating in the study.
The main inclusion criteria were patients between the ages of 18 and 70 years, hypertension, and body mass index (BMI) ranging from 24 to 40 kg/m2. The exclusion criteria were systolic blood pressure (SBP) ≥ 180 mmHg or diastolic blood pressure (DBP) ≥ 120 mmHg, type 1 or 2 diabetes with a history of severe hypoglycemic episodes, pregnancy or breastfeeding, usage of glucagon-like peptide 1 receptor agonists, weight loss > 5 kg within the past 3 months or previous weight loss surgery, and inability to adhere to the dietary protocol.
Of the 294 participants screened for eligibility, 205 were randomized in a 1:1 ratio to the IER group (n = 102) or the CER group (n = 103), stratified by sex and BMI (as overweight or obese). All participants were required to have a stable medication regimen and weight in the 3 months prior to enrollment and not to use weight-loss drugs or vitamin supplements for the duration of the study. Researchers and participants were not blinded to the study group assignment.
Interventions. Participants randomly assigned to the IER group followed a 5:2 eating pattern: a very-low-energy diet of 500-600 kcal for 2 days of the week along with their usual diet for the other 5 days. The 2 days of calorie restriction could be consecutive or nonconsecutive, with a minimum of 0.8 g supplemental protein per kg of body weight per day, in accordance with the 2016 Dietary Guidelines for Chinese Residents. The CER group was advised to consume 1000 kcal/day for women and 1200 kcal/day for men on a 7-day energy restriction. That is, they were prescribed a daily 25% restriction based on the general principles of a Mediterranean-type diet (30% fat, 45-50% carbohydrate, and 20-25% protein).
Both groups received dietary education from a qualified dietitian and were recommended to maintain their current daily activity levels throughout the trial. Written dietary information brochures with portion advice and sample meal plans were provided to improve compliance in each group. All participants received a digital cooking scale to weigh foods to ensure accuracy of intake and were required to keep a food diary while following the recommended recipe on 2 days/week during calorie restriction to help with adherence. No food was provided. All participants were followed up by regular outpatient visits to both cardiologists and dietitians once a month. Diet checklists, activity schedules, and weight were reviewed to assess compliance with dietary advice at each visit.
Of note, participants were encouraged to measure and record their BP twice daily, and if 2 consecutive BP readings were < 110/70 mmHg and/or accompanied by hypotensive episodes with symptoms (dizziness, nausea, headache, and fatigue), they were asked to contact the investigators directly. Antihypertensive medication changes were then made in consultation with cardiologists. In addition, a medication management protocol (ie, doses of antidiabetic medications, including insulin and sulfonylurea) was designed to avoid hypoglycemia. Medication could be reduced in the CER group based on the basal dose at the endocrinologist’s discretion. In the IER group, insulin and sulfonylureas were discontinued on calorie restriction days only, and long-acting insulin was discontinued the night before the IER day. Insulin was not to be resumed until a full day’s caloric intake was achieved.
Measures and analysis. The primary outcomes of this study were changes in BP and weight (measured using an automatic digital sphygmomanometer and an electronic scale), and the secondary outcomes were changes in body composition (assessed by dual-energy x-ray absorptiometry scanning), as well as glycosylated hemoglobin A1c (HbA1c) levels and blood lipids after 6 months. All outcome measures were recorded at baseline and at each monthly visit. Incidence rates of hypoglycemia were based on blood glucose (defined as blood glucose < 70 mg/dL) and/or symptomatic hypoglycemia (symptoms of sweating, paleness, dizziness, and confusion). Two cardiologists who were blind to the patients’ diet condition measured and recorded all pertinent clinical parameters and adjudicated serious adverse events.
Data were compared using independent-samples t-tests or the Mann–Whitney U test for continuous variables, and Pearson’s χ2 test or Fisher’s exact test for categorial variables as appropriate. Repeated-measures ANOVA via a linear mixed model was employed to test the effects of diet, time, and their interaction. In subgroup analyses, differential effects of the intervention on the primary outcomes were evaluated with respect to patients’ level of education, domicile, and sex based on the statistical significance of the interaction term for the subgroup of interest in the multivariate model. Analyses were performed based on completers and on an intention-to-treat principle.
Main results. Among the 205 randomized participants, 118 were women and 87 were men; mean (SD) age was 50.5 (8.8) years; mean (SD) BMI was 28.7 (2.6); mean (SD) SBP was 143 (10) mmHg; and mean (SD) DBP was 91 (9) mmHg. At the end of the 6-month intervention, 173 (84.4%) completed the study (IER group: n = 88; CER group: n = 85). Both groups had similar dropout rates at 6 months (IER group: 14 participants [13.7%]; CER group: 18 participants [17.5%]; P = .83) and were well matched for baseline characteristics except for triglyceride levels.
In the completers analysis, both groups experienced significant reductions in weight (mean [SEM]), but there was no difference between treatment groups (−7.2 [0.6] kg in the IER group vs −7.1 [0.6] kg in the CER group; diet by time P = .72). Similarly, the change in SBP and DBP achieved was statistically significant over time, but there was also no difference between the dietary interventions (−8 [0.7] mmHg in the IER group vs −8 [0.6] mmHg in the CER group, diet by time P = .68; −6 [0.6] mmHg in the IER group vs −6 [0.5] mmHg in the CER group, diet by time P = .53]. Subgroup analyses of the association of the intervention with weight, SBP and DBP by sex, education, and domicile showed no significant between-group differences.
All measures of body composition decreased significantly at 6 months with both groups experiencing comparable reductions in total fat mass (−5.5 [0.6] kg in the IER group vs −4.8 [0.5] kg in the CER group, diet by time P = .08) and android fat mass (−1.1 [0.2] kg in the IER group vs −0.8 [0.2] kg in the CER group, diet by time P = .16). Of note, participants in the CER group lost significantly more total fat-free mass than did participants in the IER group (mean [SEM], −2.3 [0.2] kg vs −1.7 [0.2] kg; P = .03], and there was a trend toward a greater change in total fat mass in the IER group (P = .08). The secondary outcome of mean (SEM) HbA1c (−0.2% [0.1%]) and blood lipid levels (triglyceride level, −1.0 [0.3] mmol/L; total cholesterol level, −0.9 [0.2] mmol/L; low-density lipoprotein cholesterol level, −0.9 [0.2 mmol/L; high-density lipoprotein cholesterol level, 0.7 [0.3] mmol/L] improved with weight loss (P < .05), with no differences between groups (diet by time P > .05).
The intention-to-treat analysis demonstrated that IER and CER are equally effective for weight loss and blood pressure control: both groups experienced significant reductions in weight, SBP, and DBP, but with no difference between treatment groups – mean (SEM) weight change with IER was −7.0 (0.6) kg vs −6.8 (0.6) kg with CER; the mean (SEM) SBP with IER was −7 (0.7) mmHg vs −7 (0.6) mmHg with CER; and the mean (SEM) DBP with IER was −6 (0.5) mmHg vs −5 (0.5) mmHg with CER, (diet by time P = .62, .39, and .41, respectively). There were favorable improvements in
Conclusion. A 2-day severe energy restriction with 5 days of habitual eating compared to 7 days of CER provides an acceptable alternative for BP control and weight loss in overweight and obese individuals with hypertension after 6 months. IER may offer a useful alternative strategy for this population, who find continuous weight-loss diets too difficult to maintain.
Commentary
Globally, obesity represents a major health challenge as it substantially increases the risk of diseases such as hypertension, type 2 diabetes, and coronary heart disease.1 Lifestyle modifications, including weight loss and increased physical activity, are recommended in major guidelines as a first-step intervention in the treatment of hypertensive patients.2 However, lifestyle and behavioral interventions aimed at reducing calorie intake through low-calorie dieting is challenging as it is dependent on individual motivation and adherence to a strict, continuous protocol. Further, CER strategies have limited effectiveness because complex and persistent hormonal, metabolic, and neurochemical adaptations defend against weight loss and promote weight regain.3-4 IER has drawn attention in the popular media as an alternative to CER due to its feasibility and even potential for higher rates of compliance.5
This study adds to the literature as it is the first randomized controlled trial (to the knowledge of the authors at the time of publication) to explore 2 forms of energy restriction – CER and IER – and their impact on weight loss, BP, body composition, HbA1c, and blood lipid levels in overweight and obese patients with high blood pressure. Results from this study showed that IER is as effective as, but not superior to, CER (in terms of the outcomes measures assessed). Specifically, findings highlighted that the 5:2 diet is an effective strategy and noninferior to that of daily calorie restriction for BP and weight control. In addition, both weight loss and BP reduction were greater in a subgroup of obese compared with overweight participants, which indicates that obese populations may benefit more from energy restriction. As the authors highlight, this study both aligns with and expands on current related literature.
This study has both strengths and limitations, especially with regard to the design and data analysis strategy. A key strength is the randomized controlled trial design which enables increased internal validity and decreases several sources of bias, including selection bias and confounding. In addition, it was also designed as a pragmatic trial, with the protocol reflecting efforts to replicate the real-world environment by not supplying meal replacements or food. Notably, only 9 patients could not comply with the protocol, indicating that acceptability of the diet protocol was high. However, as this was only a 6-month long study, further studies are needed to determine whether a 5:2 diet is sustainable (and effective) in the long-term compared with CER, which the authors highlight. The study was also adequately powered to detect clinically meaningful differences in weight loss and SBP, and appropriate analyses were performed on both the basis of completers and on an intention-to-treat principle. However, further studies are needed that are adequately powered to also detect clinically meaningful differences in the other measures, ie, body composition, HbA1c, and blood lipid levels. Importantly, generalizability of findings from this study is limited as the study population comprises only Chinese adults, predominately middle-aged, overweight, and had mildly to moderately elevated SBP and DBP, and excluded diabetic patients. Thus, findings are not necessarily applicable to individuals with highly elevated blood pressure or poorly controlled diabetes.
Applications for Clinical Practice
Results of this study demonstrated that IER is an effective alternative diet strategy for weight loss and blood pressure control in overweight and obese patients with hypertension and is comparable to CER. This is relevant for clinical practice as IER may be easier to maintain in this population compared to continuous weight-loss diets. Importantly, both types of calorie restriction require clinical oversight as medication changes and periodic monitoring of hypotensive and hypoglycemic episodes are needed. Clinicians should consider what is feasible and sustainable for their patients when recommending intermittent energy restriction.
Financial disclosures: None.
Study Overview
Objective. To compare the effects of intermittent energy restriction (IER) with those of continuous energy restriction (CER) on blood pressure control and weight loss in overweight and obese patients with hypertension during a 6-month period.
Design. Randomized controlled trial.
Settings and participants. The trial was conducted at the Affiliated Hospital of Jiaxing University from June 1, 2020, to April 30, 2021. Chinese adults were recruited using advertisements and flyers posted in the hospital and local communities. Prior to participation in study activities, all participants gave informed consent prior to recruitment and were provided compensation in the form of a $38 voucher at 3 and 6 months for their time for participating in the study.
The main inclusion criteria were patients between the ages of 18 and 70 years, hypertension, and body mass index (BMI) ranging from 24 to 40 kg/m2. The exclusion criteria were systolic blood pressure (SBP) ≥ 180 mmHg or diastolic blood pressure (DBP) ≥ 120 mmHg, type 1 or 2 diabetes with a history of severe hypoglycemic episodes, pregnancy or breastfeeding, usage of glucagon-like peptide 1 receptor agonists, weight loss > 5 kg within the past 3 months or previous weight loss surgery, and inability to adhere to the dietary protocol.
Of the 294 participants screened for eligibility, 205 were randomized in a 1:1 ratio to the IER group (n = 102) or the CER group (n = 103), stratified by sex and BMI (as overweight or obese). All participants were required to have a stable medication regimen and weight in the 3 months prior to enrollment and not to use weight-loss drugs or vitamin supplements for the duration of the study. Researchers and participants were not blinded to the study group assignment.
Interventions. Participants randomly assigned to the IER group followed a 5:2 eating pattern: a very-low-energy diet of 500-600 kcal for 2 days of the week along with their usual diet for the other 5 days. The 2 days of calorie restriction could be consecutive or nonconsecutive, with a minimum of 0.8 g supplemental protein per kg of body weight per day, in accordance with the 2016 Dietary Guidelines for Chinese Residents. The CER group was advised to consume 1000 kcal/day for women and 1200 kcal/day for men on a 7-day energy restriction. That is, they were prescribed a daily 25% restriction based on the general principles of a Mediterranean-type diet (30% fat, 45-50% carbohydrate, and 20-25% protein).
Both groups received dietary education from a qualified dietitian and were recommended to maintain their current daily activity levels throughout the trial. Written dietary information brochures with portion advice and sample meal plans were provided to improve compliance in each group. All participants received a digital cooking scale to weigh foods to ensure accuracy of intake and were required to keep a food diary while following the recommended recipe on 2 days/week during calorie restriction to help with adherence. No food was provided. All participants were followed up by regular outpatient visits to both cardiologists and dietitians once a month. Diet checklists, activity schedules, and weight were reviewed to assess compliance with dietary advice at each visit.
Of note, participants were encouraged to measure and record their BP twice daily, and if 2 consecutive BP readings were < 110/70 mmHg and/or accompanied by hypotensive episodes with symptoms (dizziness, nausea, headache, and fatigue), they were asked to contact the investigators directly. Antihypertensive medication changes were then made in consultation with cardiologists. In addition, a medication management protocol (ie, doses of antidiabetic medications, including insulin and sulfonylurea) was designed to avoid hypoglycemia. Medication could be reduced in the CER group based on the basal dose at the endocrinologist’s discretion. In the IER group, insulin and sulfonylureas were discontinued on calorie restriction days only, and long-acting insulin was discontinued the night before the IER day. Insulin was not to be resumed until a full day’s caloric intake was achieved.
Measures and analysis. The primary outcomes of this study were changes in BP and weight (measured using an automatic digital sphygmomanometer and an electronic scale), and the secondary outcomes were changes in body composition (assessed by dual-energy x-ray absorptiometry scanning), as well as glycosylated hemoglobin A1c (HbA1c) levels and blood lipids after 6 months. All outcome measures were recorded at baseline and at each monthly visit. Incidence rates of hypoglycemia were based on blood glucose (defined as blood glucose < 70 mg/dL) and/or symptomatic hypoglycemia (symptoms of sweating, paleness, dizziness, and confusion). Two cardiologists who were blind to the patients’ diet condition measured and recorded all pertinent clinical parameters and adjudicated serious adverse events.
Data were compared using independent-samples t-tests or the Mann–Whitney U test for continuous variables, and Pearson’s χ2 test or Fisher’s exact test for categorial variables as appropriate. Repeated-measures ANOVA via a linear mixed model was employed to test the effects of diet, time, and their interaction. In subgroup analyses, differential effects of the intervention on the primary outcomes were evaluated with respect to patients’ level of education, domicile, and sex based on the statistical significance of the interaction term for the subgroup of interest in the multivariate model. Analyses were performed based on completers and on an intention-to-treat principle.
Main results. Among the 205 randomized participants, 118 were women and 87 were men; mean (SD) age was 50.5 (8.8) years; mean (SD) BMI was 28.7 (2.6); mean (SD) SBP was 143 (10) mmHg; and mean (SD) DBP was 91 (9) mmHg. At the end of the 6-month intervention, 173 (84.4%) completed the study (IER group: n = 88; CER group: n = 85). Both groups had similar dropout rates at 6 months (IER group: 14 participants [13.7%]; CER group: 18 participants [17.5%]; P = .83) and were well matched for baseline characteristics except for triglyceride levels.
In the completers analysis, both groups experienced significant reductions in weight (mean [SEM]), but there was no difference between treatment groups (−7.2 [0.6] kg in the IER group vs −7.1 [0.6] kg in the CER group; diet by time P = .72). Similarly, the change in SBP and DBP achieved was statistically significant over time, but there was also no difference between the dietary interventions (−8 [0.7] mmHg in the IER group vs −8 [0.6] mmHg in the CER group, diet by time P = .68; −6 [0.6] mmHg in the IER group vs −6 [0.5] mmHg in the CER group, diet by time P = .53]. Subgroup analyses of the association of the intervention with weight, SBP and DBP by sex, education, and domicile showed no significant between-group differences.
All measures of body composition decreased significantly at 6 months with both groups experiencing comparable reductions in total fat mass (−5.5 [0.6] kg in the IER group vs −4.8 [0.5] kg in the CER group, diet by time P = .08) and android fat mass (−1.1 [0.2] kg in the IER group vs −0.8 [0.2] kg in the CER group, diet by time P = .16). Of note, participants in the CER group lost significantly more total fat-free mass than did participants in the IER group (mean [SEM], −2.3 [0.2] kg vs −1.7 [0.2] kg; P = .03], and there was a trend toward a greater change in total fat mass in the IER group (P = .08). The secondary outcome of mean (SEM) HbA1c (−0.2% [0.1%]) and blood lipid levels (triglyceride level, −1.0 [0.3] mmol/L; total cholesterol level, −0.9 [0.2] mmol/L; low-density lipoprotein cholesterol level, −0.9 [0.2 mmol/L; high-density lipoprotein cholesterol level, 0.7 [0.3] mmol/L] improved with weight loss (P < .05), with no differences between groups (diet by time P > .05).
The intention-to-treat analysis demonstrated that IER and CER are equally effective for weight loss and blood pressure control: both groups experienced significant reductions in weight, SBP, and DBP, but with no difference between treatment groups – mean (SEM) weight change with IER was −7.0 (0.6) kg vs −6.8 (0.6) kg with CER; the mean (SEM) SBP with IER was −7 (0.7) mmHg vs −7 (0.6) mmHg with CER; and the mean (SEM) DBP with IER was −6 (0.5) mmHg vs −5 (0.5) mmHg with CER, (diet by time P = .62, .39, and .41, respectively). There were favorable improvements in
Conclusion. A 2-day severe energy restriction with 5 days of habitual eating compared to 7 days of CER provides an acceptable alternative for BP control and weight loss in overweight and obese individuals with hypertension after 6 months. IER may offer a useful alternative strategy for this population, who find continuous weight-loss diets too difficult to maintain.
Commentary
Globally, obesity represents a major health challenge as it substantially increases the risk of diseases such as hypertension, type 2 diabetes, and coronary heart disease.1 Lifestyle modifications, including weight loss and increased physical activity, are recommended in major guidelines as a first-step intervention in the treatment of hypertensive patients.2 However, lifestyle and behavioral interventions aimed at reducing calorie intake through low-calorie dieting is challenging as it is dependent on individual motivation and adherence to a strict, continuous protocol. Further, CER strategies have limited effectiveness because complex and persistent hormonal, metabolic, and neurochemical adaptations defend against weight loss and promote weight regain.3-4 IER has drawn attention in the popular media as an alternative to CER due to its feasibility and even potential for higher rates of compliance.5
This study adds to the literature as it is the first randomized controlled trial (to the knowledge of the authors at the time of publication) to explore 2 forms of energy restriction – CER and IER – and their impact on weight loss, BP, body composition, HbA1c, and blood lipid levels in overweight and obese patients with high blood pressure. Results from this study showed that IER is as effective as, but not superior to, CER (in terms of the outcomes measures assessed). Specifically, findings highlighted that the 5:2 diet is an effective strategy and noninferior to that of daily calorie restriction for BP and weight control. In addition, both weight loss and BP reduction were greater in a subgroup of obese compared with overweight participants, which indicates that obese populations may benefit more from energy restriction. As the authors highlight, this study both aligns with and expands on current related literature.
This study has both strengths and limitations, especially with regard to the design and data analysis strategy. A key strength is the randomized controlled trial design which enables increased internal validity and decreases several sources of bias, including selection bias and confounding. In addition, it was also designed as a pragmatic trial, with the protocol reflecting efforts to replicate the real-world environment by not supplying meal replacements or food. Notably, only 9 patients could not comply with the protocol, indicating that acceptability of the diet protocol was high. However, as this was only a 6-month long study, further studies are needed to determine whether a 5:2 diet is sustainable (and effective) in the long-term compared with CER, which the authors highlight. The study was also adequately powered to detect clinically meaningful differences in weight loss and SBP, and appropriate analyses were performed on both the basis of completers and on an intention-to-treat principle. However, further studies are needed that are adequately powered to also detect clinically meaningful differences in the other measures, ie, body composition, HbA1c, and blood lipid levels. Importantly, generalizability of findings from this study is limited as the study population comprises only Chinese adults, predominately middle-aged, overweight, and had mildly to moderately elevated SBP and DBP, and excluded diabetic patients. Thus, findings are not necessarily applicable to individuals with highly elevated blood pressure or poorly controlled diabetes.
Applications for Clinical Practice
Results of this study demonstrated that IER is an effective alternative diet strategy for weight loss and blood pressure control in overweight and obese patients with hypertension and is comparable to CER. This is relevant for clinical practice as IER may be easier to maintain in this population compared to continuous weight-loss diets. Importantly, both types of calorie restriction require clinical oversight as medication changes and periodic monitoring of hypotensive and hypoglycemic episodes are needed. Clinicians should consider what is feasible and sustainable for their patients when recommending intermittent energy restriction.
Financial disclosures: None.
1. Blüher M. Obesity: global epidemiology and pathogenesis. Nat Rev Endocrinol. 2019;15(5):288-298. doi:10.1038/s41574-019-0176-8
2. Unger T, Borghi C, Charchar F, et al. 2020 International Society of Hypertension Global hypertension practice guidelines. J Hypertens. 2020;38(6):982-1004. doi:10.1097/HJH.0000000000002453
3. Müller MJ, Enderle J, Bosy-Westphal A. Changes in Energy Expenditure with Weight Gain and Weight Loss in Humans. Curr Obes Rep. 2016;5(4):413-423. doi:10.1007/s13679-016-0237-4
4. Sainsbury A, Wood RE, Seimon RV, et al. Rationale for novel intermittent dieting strategies to attenuate adaptive responses to energy restriction. Obes Rev. 2018;19 Suppl 1:47–60. doi:10.1111/obr.12787
5. Davis CS, Clarke RE, Coulter SN, et al. Intermittent energy restriction and weight loss: a systematic review. Eur J Clin Nutr. 2016;70(3):292-299. doi:10.1038/ejcn.2015.195
1. Blüher M. Obesity: global epidemiology and pathogenesis. Nat Rev Endocrinol. 2019;15(5):288-298. doi:10.1038/s41574-019-0176-8
2. Unger T, Borghi C, Charchar F, et al. 2020 International Society of Hypertension Global hypertension practice guidelines. J Hypertens. 2020;38(6):982-1004. doi:10.1097/HJH.0000000000002453
3. Müller MJ, Enderle J, Bosy-Westphal A. Changes in Energy Expenditure with Weight Gain and Weight Loss in Humans. Curr Obes Rep. 2016;5(4):413-423. doi:10.1007/s13679-016-0237-4
4. Sainsbury A, Wood RE, Seimon RV, et al. Rationale for novel intermittent dieting strategies to attenuate adaptive responses to energy restriction. Obes Rev. 2018;19 Suppl 1:47–60. doi:10.1111/obr.12787
5. Davis CS, Clarke RE, Coulter SN, et al. Intermittent energy restriction and weight loss: a systematic review. Eur J Clin Nutr. 2016;70(3):292-299. doi:10.1038/ejcn.2015.195