What is the real goal of weight loss? In health care, reducing excess body fat is known to improve many complications faced by patients with obesity. Even modest to moderate weight loss contributes to improvements in health. Normalizing body weight is not required.
While our culture promotes an ideal body size, in the health care setting, our attention must focus on achieving health improvement. We need to be more tolerant of variations in body size if patients are healthy. Of note, varying amounts of weight loss produce improvement in the different complications of obesity, so the amount of weight loss required for improving one condition differs from that required to improve another condition.
When we prescribe weight loss for health improvement, we are trying to reduce both the mechanical burden of fat and the excess ectopic and visceral body fat that is driving disease. The good news about the physiology of weight loss is that we do not need to attain a body mass index (BMI) of 25 or even 30 to have health improvement. The excess abnormal body fat is the first to go!
Losing weight causes a disproportional reduction in ectopic and visceral fat depots. With a 5% weight loss, visceral fat is reduced by 9%. With 16% weight loss, visceral fat is reduced by 30%. Clearing of liver fat is even more dramatic. With 16% weight loss, 65% of liver fat is cleared.
Because ectopic abnormal fat is cleared preferentially with weight loss, it affects different tissues with varying amounts of weight loss.
Weight loss and diabetes
A close relationship exists between weight loss and insulin sensitivity. With just 5% weight loss, insulin sensitivity in the liver and adipose tissue is greatly improved, but while muscle insulin sensitivity is improved at just 5% weight loss, it continues to improve with further weight loss. Indeed, weight loss has enormous benefits in improving glycemia in prediabetes and diabetes.
In patients with impaired glucose tolerance, weight loss of 10% can eliminate progression to type 2 diabetes. In patients with type 2 diabetes who still have beta-cell reserve, 15% weight loss can produce diabetes remission – normoglycemia without diabetes medications.
Weight loss and cardiovascular risk factors
Even very small amounts of weight loss – 3% – can improve triglycerides and glycemia. It takes 5% weight loss to show benefits in systolic and diastolic blood pressure, as well as in HDL and LDL cholesterol levels. For all of these, additional weight loss brings more improvement. Inflammatory markers are more difficult. It takes 10%-15% weight loss to improve most of these – for example, C-reactive protein.
Weight loss and other complications
It takes 10% or more weight loss to demonstrate improvements in symptoms in obstructive sleep apnea and gastroesophageal reflux disease. For knee pain, the relationship to improvement is not based on achieving a percentage loss. Each pound of weight lost can result in a fourfold reduction in the load exerted on the knee per step during daily activities, but it is important to reduce weight before there is structural damage, because weight loss can’t repair damaged knee joints. Moderate weight loss (5%-10%) produces improvements in quality-of-life measures, in urinary stress incontinence symptoms, and in measures of sexual function. It probably takes 15% or more weight loss to demonstrate improvement in cardiovascular events.