Nutritional Pearls: Genetically Based Weight Loss Plans: Not Yet

Roger is a 46-year-old man who is struggling to lose weight. Recently, he read several news articles online that discussed the use of genetics to determine what diets individuals are more likely to see results from and is curious if this is something that he could try.

How do you advise your patient?
(Answer and discussion on next page)

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Answer: At the present, it is not possible to genetically determine which diets will work for which individuals.

Recent advances in genetic engineering and genetically-customized treatments for various conditions are very exciting, with promising research being done in the fields of cancer and red blood cell disorders, among others. With obesity being such a significant health issue, there has also been research directed toward the interaction of genotype and weight loss: there is research to suggest that specific genotypes may make one more easily lose weight with a low-carbohydrate diet, for example, or with a low-fat diet.

Wouldn't it be fantastic to be able to tell your patients that their genetics predisposed them to be more likely to lose weight with a specific type of diet?

The Research

Building on a previous, retrospective study that identified a low-fat-diet genotype (those predisposed to lose more weight on a low-fat diet) and a low-carbohydrate genotype (those predisposed to lose more weight on a low-carbohydrate diet), a research team at Stanford University in California designed a weight loss study to examine those genotypes prospectively.

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Rather than identifying an individual's genotype after weight loss, the authors in this study recruited individuals to participate in their weight-loss study and identified the individual's genetic propensity before randomly assigning them to a low-carbohydrate or low-fat diet.

The 481 men and women who completed the 12-month study, who were overweight or obese but otherwise generally healthy, were randomly assigned, regardless of their determined genotype, to either a low-fat or low-carbohydrate diet and were supported with weekly group dietary counseling sessions weekly for the first 8 weeks, then every other week for the next 2 months, then every 3 weeks until the 6th month of the study, then monthly until the end of the study (at 12 months).

The participants' diets emphasized high-quality foods and beverages, maximizing vegetable intake, minimizing added sugars and refined flours, and focusing on foods that were "minimally processed, nutrient dense, and prepared at home whenever possible." They were not instructed to cut their caloric intake by any specific amount but were encouraged to meet physical activity recommendations of 30 minutes per day.

At months 3, 6, and 12, the participants responded to dietary questionnaires (to make sure they were sticking to their assigned diets) and underwent blood and insulin tolerance tests along with having their weight and waist circumferences measured.

The Results

The results were not exciting. Not only was there no statistically significant difference between the amount of weight lost on a low-fat versus low-carb diet, within the 2 groups the participants' genotype (low-fat or low-carb) made no statistical difference in how much weight they lost: for example, those with a genotype considered to be more conducive to losing weight on a low-fat diet lost no more weight on a low-fat diet than they did on a low-carb diet (and vice versa).

What’s the Take-Home?

It's certainly possible that at some point in the future we may know more about which type of diet will work better for your patients, genetically speaking. That time is not now. Until then, your best bet is to counsel your patients on consuming high-quality calories through a diet that we know people can stick with for the long term: a Mediterranean-style diet.

Reference:

Effect of low-fat vs low-carbohydrate diet on 12-month weight loss in overweight adults and the association with genotype pattern or insulin secretion. JAMA. 2018;319(7):667-679.