By Joseph E. Scherger, MD, MPH

Core Faculty, Eisenhower Health Family Medicine Residency Program, Eisenhower Health Center, La Quinta, CA; Clinical Professor, Keck School of Medicine, University of Southern California, Los Angeles

Dr. Scherger reports no financial relationships relevant to this field of study.

SYNOPSIS: Consistent with the role of insulin and carbohydrate intake, a low-carbohydrate diet increases energy expenditure and facilitates the maintenance of weight loss.

SOURCE: Ebbeling CB, et al. Effects of a low carbohydrate diet on energy expenditure during weight loss maintenance: Randomized trial. BMJ 2018;363:k4583.

Ebbeling et al conducted this randomized, controlled trial at two sites in Framingham, MA, between August 2014 and May 2017. The group evaluated the recent realization that with most weight loss diets, hunger increases and energy expenditure decreases. These physiologic adaptions work against long-term weight loss. Most standard weight loss diets are calorie-restricted, with about 60% of calories coming from carbohydrates. The purpose of the study was to assess metabolic expenditure at rest using three different carefully controlled diets that were high in carbohydrates (60% of calories), medium in carbohydrates (40% of calories), and low in carbohydrates (20% of calories) during the maintenance phase of a weight loss program. Investigators recruited 164 subjects aged 18-65 years. Participants started the study following the same diet to accomplish 2 kg of weight loss. The composition of this “run-in” diet was 45% carbohydrates, 30% fats, and 25% proteins. The subjects were randomized to one of the three diet types. Protein intake was controlled to 20% of calories in all three groups so that subjects on 60% carbohydrates received 20% of calories from fat, those on 40% carbohydrates received 40% from fat, and those on 20% carbohydrates received 60% from fat. The testing phase lasted 20 weeks. The results showed that subjects on the lower-carbohydrate diets showed a linear increase in energy expenditure at rest and a linear benefit in maintaining weight reduction. Ghrelin, the hormone that increases appetite, was significantly lower in subjects on the low-carbohydrate diet. In addition, insulin levels were lower with low-carbohydrate diets.

COMMENTARY

Forty years ago, clinical guidelines in nutrition moved to a low-fat, complex carbohydrate diet. The American food supply became awash in refined carbohydrates. The “green revolution” that started in the 1970s shifted American agriculture to wheat and corn as dominant crops for human consumption and feed for animals. Since 1980, there has been an epidemic of overweight, obesity, and type 2 diabetes.1 By 2001, scholars began to question the low-fat recommendations and suggested that sugar and carbohydrates were the real problem. Despite resistance from the food industry that makes its greatest profits from high-carbohydrate foods, scientific evidence is growing that carbohydrates drive hunger and weight gain.2 We have learned that once obtained, the body can hold on to fat and get it back once lost through changes in metabolism.3 Research has shown that the most effective way to break this problem and maintain low weight is through low-carbohydrate nutrition and remaining in a state of ketosis for at least part of the day. This is facilitated by intermittent fasting, which further lowers insulin secretion. Low-carbohydrate nutrition and weight loss programs are emerging, including in academic centers. Look for programs in your area that can provide this patient education and incorporate low-carbohydrate nutrition into your practice.

REFERENCES

  1. Ng M, et al. Global, regional, and national prevalence of overweight and obesity in children and adults during 1980-2013: A systematic analysis for the Global Burden of Disease Study 2013. Lancet 2014;384:766-781.
  2. Ludwig DS. Always Hungry?: Conquer Cravings, Retrain Your Fat Cells, and Lose Weight Permanently. New York: Hachette Book Group; 2016.
  3. Fothergill E, et al. Persistent metabolic adaption 6 years after “The Biggest Loser” competition. Obesity (Silver Spring) 2016;24:1612-1619.