The Pick 'N' Mix Diet

A Stanford University study finds no biological reason to opt for one weight-loss diet over another.

- Nicky Pellegrino

The low-carb, high-fat ketogenic diet is all the rage. So if you want to lose weight and be healthier should you be on it? Or would you be better to go paleo, vegan, low-fat or sugar-free, or eat according to your blood type or genes? Never has there been so much confusion about the best way to fuel our bodies, and meanwhile we keep getting fatter.

Christopher Gardner, the director of nutrition studies at Stanford University in California, had a couple of theories about why some diets might work for certain people and not others. The first was related to genes. Three genotypes had been identified that appeared, from a small study of overweight women, to influence whether they shed more kilos on a low-fat or a low-carb diet.

Gardner embarked on a second, larger trial with 609 overweight adults aged 18 to 50 who cut back on fat or carbs for a year depending on their genotype. All were encouraged to eat the healthiest possible versions of low-fat or low-carb diets, avoiding sugar and refined grains. They attended 22 nutrition sessions, were taught to eat mindfully, avoid highly processed foods, consume lots of vegetables and prepare meals at home. They weren’t instructed to cut or count calories.

By the end of the trial, people in both of the groups lost an average of 5-6kg – it made no difference which eating plan they followed or what genotype they had.

The publication of Gardner’s Dietfits study earlier this year resulted in headlines around the world suggesting that personalised diets don’t work and DNA-matching makes no difference. But Gardner says it’s not as simple as that.

“Here’s the problem: there are dozens, maybe hundreds, of genes related to obesity. There are so many that one study couldn’t possibly look at them all.”