We hear a lot about the obesity epidemic in the United States and around the world. Scientists acknowledge that this has occurred too rapidly to be explained by changes in genetics. Instead, nutrition scientists often turn to the energy balance model: people eating more calories than they expend. However, this dietary dogma on weight gain leaves too many questions unanswered, according to our guests. Instead, they’d like to see a change in the paradigm regarding weight gain.
Many people report that they have gained weight during the pandemic. In fact, a survey from the American Psychological Association found that 42 percent of adults reported gaining weight, an average of about 29 pounds.
In addition, a small study published in JAMA Network Open used more than 7,000 measurements from 269 participants between February and June 2020. A lot of people were in lockdown during that time, and participants gained an average of 1.5 pounds per month. But why? Was it the restriction on activity outside the home? Did people snack more due to anxiety or boredom? Or did the type of food they were eating encourage weight gain?
Most nutrition experts blame weight gain on people eating too much and being too sedentary–calories in exceeding calories out. However, a group of eminent nutrition researchers and commentators have recently questioned that model as too simplistic. They published their commentary in the American Journal of Clinical Nutrition as “The carbohydrate-insulin model: a physiological perspective on the obesity pandemic” (September 13, 2021). In it, they suggested that the old energy balance model (calories in vs. calories out) should be compared to the carbohydrate-insulin model.
This model posits that highly processed carbohydrates (think Halloween candy) drives blood sugar up so rapidly that insulin responds by stashing the energy in fat cells. As a result, people might feel hungry even though they are adding fat.
We talk with two of the authors of this review, which calls for rigorous research “to compare the validity of these 2 models, which have substantially different implications for obesity management…” How does challenging dietary dogma on weight gain affect what you might eat?
David S. Ludwig, MD, PhD, is an endocrinologist and researcher. He is Professor of Pediatrics at Harvard Medical School and Professor of Nutrition at the Harvard T.H. Chan School of Public Health. Dr. Ludwig also co-directs the New Balance Foundation Obesity Prevention Center at Boston Children’s Hospital. His research focuses on how food affects hormones, metabolism, body weight, and well-being. Dr. Ludwig is the author of several books, including the NYTs bestseller Always Hungry?
Dr. Ludwig's website is https://www.childrenshospital.org/research/researchers/l/david-ludwig The link to the paper is: https://doi.org/10.1093/ajcn/nqab270 The photograph is of Dr. Ludwig.
Walter C. Willett, MD, DrPH, is a physician and epidemiologist. He is Professor of Epidemiology and Nutrition at the Harvard T.H. Chan School of Public Health, where he served as Chair of the Department of Nutrition for 25 years. He is also Professor of Medicine at Harvard Medical School.
Much of his work has been on the development of methods, using both questionnaire and biochemical approaches, to study the effects of diet on the occurrence of major diseases. Dr. Willett has published over 2,000 research papers, primarily on lifestyle risk factors for heart disease and cancer, and has written the textbook, Nutritional Epidemiology, published by Oxford University Press. He also has written four books for the general public, including Eat, Drink and Be Healthy. Dr. Willett is the most cited nutritional scientist internationally.
He is a member of the National Academy of Medicine and the recipient of many national and international awards for his research. Dr. Willett was the very first to receive The People’s Pharmacy Award for Excellence in Research and Communication for the Public Health. Dr. Willett's website is https://www.hsph.harvard.edu/walter-willett/
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