Calorie counting has always been ingrained in the prevailing nutrition and weight loss advice.
Gardner emphasizes that it's all about healthy low-fat and low-carb diets. "We told them all that we wanted them to minimize added sugar and refined grains and eat more vegetables and whole foods". They were randomly placed into one of the two dietary groups - low-carb or low-fat. It's worth noting that average fat consumption for the participants before the study started was around 87 grams a day, and average carbohydrate intake was about 247 grams. Study participants in both groups lost an average of 12-13 pounds. Previous research maintains that insulin levels or certain genes could interact with a person's type of diet and ultimately influence the effectiveness of their weight loss. Companies such as DNAFit and Helix suggest consumers pay about $100 and a simple cheek swab; the resulting genomic analysis will purportedly show them what kind of diet will keep their bodies in peak health.
Although results varied greatly among the participants - one lost 60 pounds while another gained 20 - and 200 participants dropped out before the end of the study, the results at the end were similar.
Instead, the goal was to explore which factors - genetic patterns and insulin resistance - might predict success for people on the two diets; in other words, "Which diet is best for whom?" "And those low-carb chips - don't buy them, because they're still chips and that's gaming the system'". But I was hoping to see some significant difference in the weight lost by those matched by genotype. There was also no DNA/diet interaction for waist circumference, body mass index, or body fat percentage.
"The unique thing is that we didn't ever set a number for them to follow", Gardner said.
"This study closes the door on some questions - but it opens the door to others". But there was no link whatsoever between what diet they were on and the tested genes. A spokeswoman for another leading DNA/diet company, Habit, said it agrees that DNA alone "isn't enough to develop personalized dietary recommendations" and that the company therefore factors in blood biomarkers and other information "when making personalized dietary recommendations".
Although it would seem that one group has to be wrong, a new study suggests that the battle between low-fat and low-carb diets is actually a draw - so both sides are right.
Gardner's own 2010 study, of 140 overweight women divided into various DNA and diet types, reached the same conclusion.
"We've been taught that the key to taking off the pounds is to consume fewer calories than we burn". There was still, however, vast weight loss variability among them - some dropped upward of 60 pounds, while others gained close to 15 or 20.
The participants were encouraged to meet the federal guidelines for physical activity but did not generally increase their exercise levels, Gardner said.
"We were so excited and thought this would work. It's humbling, and just underlines the importance of replication" of tantalizing preliminary findings with larger, more rigorous studies.