Carbs, fat, DNA? Weight loss is finicky, new study suggests
Avoid processed foods, sugar and eat veggies for best result
CHICAGO — A precision nutrition approach to weight loss didn’t hold up in a study using dieters’ DNA profiles.
Previous research suggested that a person’s insulin levels or certain genes could interact with different diets to influence weight loss.
Stanford University researchers examined this idea with 600 overweight adults who underwent genetic and insulin testing before being randomly assigned to reduce either fat or carbohydrates.
Gene analyses identified variations in how the body processes fats or carbohydrates, which the researchers thought would make them more likely to lose weight on a low- fat or low- carb diet.
But weight loss averaged about 6 kg ( 13 pounds) over a year, regardless of genes, insulin levels or diet type.
Also, some people lost as much as 27 kg ( 60 pounds) and others gained 6.8 kg ( 15 pounds) — more evidence that genetic characteristics and diet type appeared to make no difference.
What seemed to make a difference was healthful eating.
Participants on both diets who consumed the fewest processed foods, sugary drinks, unhealthy fats and ate the most vegetables lost the most weight.
The results suggest that “precision medicine is not as important as eating mindfully, getting rid of packaged, processed food” and avoiding unhealthy habits like eating while watching television, said lead author Christopher Gardner.
The study was published in the Journal of the American Medical Association.
Participants had health education classes and were encouraged to be physically active, but the focus was on what they ate.
They were advised to choose highquality foods but were not given suggested calorie limits or specific foods. Results are based on what they reported eating.
During the first two months, dieters in each group were told to limit carbohydrates or fats to the amount in 11/2 slices of whole- wheat bread and a handful of nuts respectively.
Both groups reduced their daily calorie intake by an average of about 500 calories. The study was wellconducted but because participants were not given specific foods and selfreported their food choices, it wasn’t rigorous enough to disprove the idea that certain genes and insulin levels may affect which types of diets lead to weight loss, said Dr. David Ludwig, a Boston Children’s Hospital obesity researcher.
Dr. Frank Hu, nutrition chief at Harvard’s School of Public Health, has called precision nutrition a promising approach and said the study wasn’t a comprehensive test of all gene variations.
“In any weight loss diets, adherence to the diet and the overall quality of the diet are probably more important than any other factors,” Hu said.
In any weight loss diets, adherence to the diet and the overall quality of the diet are probably more important than any other factors.”
Dr. Frank Hu