The Role of Diet in Managing Obesity

Mireille Serlie, MD, PhD, loves fast food. Her research seeks to understand why.

“Fast and ultra-processed foods do something to our brains that make us overeat,” says Serlie, a professor of medicine (endocrinology and metabolism) at Yale School of Medicine.

Serlie studies the effects of eating patterns and specific nutrients on the brain and the functional differences between the brains of people with obesity and those with a healthy weight.

In a Q&A, Serlie discusses eating patterns, fasting, and the importance of diet and exercise in retaining muscle mass after weight loss.

The first-line treatment of obesity in terms of dietary management is a hypocaloric diet tailored to individual preferences to increase tolerability and diet adherence. But eating patterns are also important.

In a study, when we gave healthy people extra calories from fat and sugar between meals to mimic hypercaloric snacking, we found that their liver fat increased independent of weight gain. Too much liver fat can lead to insulin resistance and an increased risk of diabetes. That research shows that eating patterns matter and can have independent negative effects on metabolic health.

Since publishing that study, I have advised patients to eat three meals a day and not snack in between. Eating later at night increases the risk of obesity, probably because of the effects of late eating on brain mechanisms of food intake. We found that during weight loss, eating most calories earlier in the day affects the brain’s dopamine system and reduces the brain’s response to pictures of unhealthy food. Therefore, I also advise people not to skip breakfast and to finish dinner before 8 p.m.

It’s also important to keep in mind that the body needs periods of fasting for all kinds of repair mechanisms to occur in our organs, including the brain. Research has shown that sufficient periods of fasting increases memory function in older people, for example.

Diets are not very successful in the long term. Within five years, most people regain up to 70 to 80% of the weight they lost during their diet. So it's great we have effective medication and metabolic surgery. But a healthy diet and exercise should be part of any obesity treatment.

Weight loss is good, but a negative energy balance also leads to muscle mass breakdown. This is inevitable and should be minimized as much as possible through diet and exercise. When taking novel anti-obesity drugs or after metabolic surgery, eating three meals a day containing enough protein is important. It is also important to monitor for deficiencies in vitamins and trace elements. Resistance exercise is essential to retain as much muscle mass as possible.

Diet composition is important, but eating patterns and timing of food intake also contribute to body weight and metabolic health. Food high in fat and sugar can affect brain mechanisms of food intake and result in eating beyond caloric need.

Yale School of Medicine’s Section of Endocrinology and Metabolism works to improve the health of individuals with endocrine and metabolic diseases by advancing scientific knowledge, applying new information to patient care, and training the next generation of physicians and scientists to become leaders in the field. To learn more, visit Endocrinology and Metabolism.