Results from a rigorous $8 million study are out!
There has been a growing area of interest in the area of Genomics and the hope that we have found the magic solution by matching a person’s DNA to a specific diet type. We had hoped it might explain why only some people manage to lose weight on a low carb diet and why some others succeed on a low fat diet (even though we know that diets are not sustainable long term and dieters tend to regain the weight initially lost!).
Despite some earlier studies claiming that genetic variants can predict whether someone has a better chance of shedding weight on a low carb diet or low fat diet, the most vigorous study so far found NO difference in weight loss between overweight people on diets that ‘matched’ their genotype and those on diet’s that didn’t.
The DIETFITS Study
The study called DIETFITS and published in the Journal of the American Medical Association by researchers at Stanford University assigned 609 overweight adults, aged 18 to 50, to either a healthy low-fat diet or healthy low carb diet. The study participants received 22-hour long dietitian sessions with education on healthy low-fat diets (eat fewer oils, fatty meat, full-fat dairy and nuts) or low carb ones (reduce cereals, grains, rice, starchy vegetable and legumes), as well as the dangers of eating mindlessly. Both groups were instructed to eat more vegetables, less processed/refined foods. This pattern of eating was held for 12 months. The researchers then analysed weight loss amongst those DNA ‘matched’’ or clashed with their assigned diet. This was based on variants in three genes called PPARG, ADRB2 and FABP2 which are involved in the fat and carbohydrate metabolism. The primary outcome was a 12-month weight change and determination of whether there were significant interactions among diet type and genotype pattern, diet and insulin secretion and diet and weight loss.
There were no significant differences in weight change among participants matched vs mismatched on their diet assignment. There was also no DNA/diet interaction for waist circumference, body mass index or fat percentage.
This is a great reminder that weight loss is a long and complex healthy journey. There are so many external factors emotional, economic, social, metabolic and other forces that may affect someone’s chance of losing weight. If you are experiencing difficulties losing weight you are not alone! However in my experience, a multidisciplinary approach with other health professional such as a Dietitian and Exercise Physiologist will assist in directing you in the right direction for real and sustainable health change!
References
Scientific American, author Sharon Begley http://www.scientificamerican.com/article/matching-dna-to-a-diet-does-not-work
Gardner C, Trepanowski J, Gobbo L et al. The Amer. Journal of the American Association. 2018.
Effect of low fat vs low carbohydrate diet on 12 month weight loss in overweight adults and the association with genotype pattern on insulin secretion. https://jamanetwork.com/journals/jama/article-abstract/2673150?redirect=true
