Obesity is a growing problem in the USA with more than 60% of the population now classified as overweight and more than 30% are obese. We tend to think of overweight people as destined to be at high risk for chronic health problems. But recent studies have highlighted that weight alone often does not determine future health. In fact, healthy people can come in all shapes and sizes.
If we compare a group of thin people to a group of obese people it is very likely that we will find more people with high blood pressure, high cholesterol, diabetes, arthritis and vascular disease in the obese group. However, we will also find people in the thin group who suffer from these conditions and many in the obese group who are still in excellent health. At Princeton Longevity Center we frequently see patients who are “obese” based on both weight and body composition analysis (percent body fat) yet they have no current medical problems.
If you are overweight the key to staying well may be your level of physical fitness.
The death rate for men and women who are thin but not physically fit is more than twice as high as for obese men and women who are fit. Across every level of body size, unfit people have a much higher death rate than those who are fit.
The graph below, from a study in the Journal of Clinical Nutrition, shows the risk of developing cardiovascular disease (CVD) according to Body-Mass Index (BMI), a common measure of weight versus height. In those who were unfit, the risk of CVD was higher with increased weight. For patients who stayed fit being at a higher weight did not raise their risk for CVD compared with those were fit and at normal weight. In fact, the overweight fit patients were at much lower risk than those at a normal weight who did not stay fit. Overall, fitness had a much bigger impact than weight.
Part of the explanation may lie in where fat can accumulate.
There are different kinds of body fat. Subcutaneous fat, the fat that you can pinch under your skin, is metabolically benign. You may not like the way it looks but it does not appear to significantly increase your risk for the health problems we typically associate with obesity.
On the other hand, visceral fat, the fat found inside the abdomen and chest around the internal organs, is very metabolically active. Visceral fat produces substances that promote inflammation, raises blood pressure and triglycerides, lower HDL levels, change hormone levels and interfere with control of blood sugar.
Measuring your weight or your BMI does not tell you whether your fat is subcutaneous or visceral fat. The only accurate way to measure visceral fat is with a CT or MRI scan.
Visceral fat appears to result from a genetic predisposition combined with a high carbohydrate diet and a sedentary lifestyle. The more you exercise, the less likely you are to have visceral fat. Fit overweight people are more likely to carry their extra weight as the much less harmful subcutaneous fat.
Many of us are frustrated with constant diets and trying to lose weight that just won’t stay off. While it may not get you back into the clothes you wore when you were 20, focusing on getting at least 150 minutes per week of exercise may help you to avoid many of the health problems that can come with being overweight. Even if you don’t lose weight, staying active will be an excellent investment in the quality of your future years.
David A Fein, MD
Princeton Longevity Center