Understanding metabolic health

What is your body’s “set point”?

There are many theories on the causes of obesity. Environmental, psychological, genetic and metabolic factors all appear to play a role in the rise of obesity. One of several theories that explains why people who are overweight often have trouble losing weight or maintaining weight loss, is called the “set point” theory. This theory suggests that our body has a complex system of hormones and other bodily signals that control appetite, digestion and metabolism. According to this theory, this system keeps our bodies at a steady weight, or “set point.” When a person reduces the amount of food they eat, the body defends the previously established “set point” as a way of coping with what seems to be a period of starvation, even among people with obesity.

Dr. David Katz, the founding director of the Yale University Prevention Research Center, says, “Throughout most of human history, calories were scarce and hard to get, so we have numerous natural defenses against starvation. We have no defenses against overeating because we never needed them before.”

Everyone’s “set point” is different, and the body manages “set point” in a similar way to how it controls cholesterol, blood pressure, and blood sugar(55). The body’s “set point” can be affected by genetic, developmental and environmental factors. Changes in any of these factors can lead to a higher “set point”, which leads to more body fat storage. For example, changes in the nutrients of the food we eat can affect our brains and lead to an increase in the amount we eat, and may increase our “set point”(55). As we gain weight, our bodies may work to defend our new weight. Our bodies are smart, and they adapt to change. But in our current environment with abundant, high-calorie food and reduced need for physical activity, it’s not always for the better. 

Why isn’t diet and exercise enough to lose weight?

Because of metabolic, environmental, and genetic factors that work against weight loss, diet and exercise alone are rarely enough to help people with obesity to lose weight and keep it off in the long run. When you go on a diet, your body thinks it’s being starved and its survival instincts kick in. As a result, your body stores energy-rich body fat, and you can’t lose weight easily. One study found that on average, a 200-pound patient trying to lose weight with diet and exercise alone would only be able to lose and keep off 4 pounds over 20 years(4). Another study found that 95% of obese people that lose weight with a rigorous weight loss program will regain the weight (or more) within 2 to 5 years.(1)

Unfortunately, your body’s hormones are working against you. When you lose weight, lower body fat levels trigger hormones that encourage the body to get back to its previous weight “set point”. A New England Journal of Medicine study showed that while dieters may initially lose weight, their bodies change the levels of hormones that encourage weight regain in response to the weight loss. These hormones increase appetite, decrease feelings of fullness, and slow down metabolism. The hormones may not return to pre-diet levels even 12 months after the initial weight loss, which may lead to weight-regain a year after dieting.(3, 53) This is a powerful defense mechanism and may explain why many weight loss attempts fail.

How does bariatric surgery help with weight loss?

Bariatric surgery helps reset the body’s ability to effectively manage weight by altering the complex relationships between metabolism and behavior. Research suggests that bariatric surgery may affect the metabolism in ways that lower the “set point”, leading to long-term weight loss. By changing the anatomy of the stomach and intestine, these surgeries affect hormonal signals, which can lead to a lower appetite, stronger feelings of fullness, and higher metabolism. These positive changes allow your body to lose weight without the internal fight to return to the higher “set point”.