Rekha B. Kumar, M.D. Responds

As a physician who specializes in hormones and weight management, I’m often asked questions about the aging process and weight gain or change in body shape over time. I meet patients with great concern over their increase in weight, loss of waistlines, and inability to lose weight with diets and exercise routines that were previously effective for them. These concerns usually lead to questions regarding metabolism and how it changes as we progress through life.

Although this topic is of particular interest to women as we enter the summer season, it should not only be a seasonal concern but a focus year-round for doctors and patients as we are in the midst of an obesity epidemic, with 38% of the U.S. population meeting criteria for the diagnosis of obesity (body mass index >30). Obesity has a tremendous impact economically on individuals and our country. Healthcare costs are approximately $1,500 higher annually for people who are overweight or obese. The U.S. government now spends more on obesity related costs than on our national defense budget.

Many of us see obesity as an extreme of the weight disorder spectrum but even just “weight creep” over one’s baseline or set point weight carries health risks. For example, an increase in one’s body weight by just 5% can have a negative impact on blood pressure, cholesterol profile, diabetes risk, joint mobility and psychological health. And the converse is true as well; when one is struggling with lofty weight loss goals, it is best to acknowledge that just loss of 5% of total body weight can lead to significant improvement in one’s health.

So, why is our weight creeping up? In order for individuals to maintain the same body weight from ages 21 to 65, we would have to match our calorie intake and expenditure within 0.2% consistently. This would be relatively straightforward if all we needed to control for was the calories we put in. Not to say that restricting intake is easy in our environment of easily accessible food, sugar sweetened drinks and snacks, and no requirements to burn calories to obtain rich food (the way our ancestors had to hunt) but the factors in this energy balance equation change over time. Our basal metabolic rate or the calories we burn at rest becomes lower after our 30s or 40s (sometimes even sooner). This occurs because we slowly start losing muscle mass and lean muscle is an important determinant of our basal metabolic rate. As this process occurs, we would have to eat less calories to match our metabolic rate over time. The challenge here is that our appetite often does not decrease, which is one of the reasons that dieting can be so challenging.

If decline of muscle is to blame, can’t we just start lifting weights? Yes! Resistance training exercises can help avoid the weight creep that sets in for all of us. By doing strength training and targeting all muscle groups including all of our core body muscles we can fight some of this weight gain off by maintaining muscle mass and thus keeping our metabolisms going. In fact, resistance training/weight lifting exercise is correlated with losing inches in your waist.

Then what about the hormones? Many patients complain that despite controlling calories, increasing both cardiovascular and weight lifting exercises, and occasionally even keeping their weight stable, that their “shape has changed.” All of their weight is carried in the abdomen or waist line. As we approach menopause and our estrogen levels fall (or if we experience an abrupt menopause due to surgery, chemotherapy etc.) we may notice more fat being stored in the abdomen. This is in part due to a concept called “insulin resistance.” We become more resistant to the hormone insulin around perimenopause, and we may make more insulin to turn the carbohydrates we eat into useful energy. That doesn’t sound like such a bad thing until we also note that insulin is a “fat storage” promoting hormone. When our insulin levels are higher, we store fat better. We have evolved this way to help “older people” survive famine and periods of food scarcity (remember that life expectancy was only 50 years of age just 100 years ago!). This adaptation for survival has turned into an unhelpful feature in our world of abundant and easily accessible calories and carbohydrates. One way we can lower our insulin levels and avoid excessive storage of belly fat is to reduce our carbohydrate intake so we don’t make as much insulin. Some baseline amount of insulin production by our pancreas is normal and in the absence of insulin production, people develop diabetes that requires insulin to be taken as a medicine. In addition to changes in insulin, our changing levels of testosterone and growth hormone may play a role in how our body shape changes over time but we do not yet recommend manipulating these hormones with medical intervention for the purpose of weight control.

To answer our initial question of “can I avoid weight creep over time?” the answer is “yes, at least partially.” We can control weight creep but we may not be able to avoid it completely and some small amount may be healthy and protective to our bodies in an emergency state. It might not be a famine we are preparing for but maybe an unexpected stress or health problem that requires us to have stored up fat to use as fuel later. I encourage women to start weight lifting early on, avoid simple sugars and focus on whole grains as a source of healthy carbohydrate, and to accept some healthy changes in body shape that may occur over time. Good health is always the goal!