Low carbs or fat—and does it matter?

fast food menus - sloppy burger with bacon

There’s not much point trying to tailor a weight loss diet to one’s genes, researchers have found

In a study that was welcomed by diet and nutrition experts, researchers enrolled 609 overweight adults in a randomised clinical trial from January 2013 through April 2015, with follow-up through May 2016.

The participants followed either a healthy low-fat (305 participants) diet or a healthy low-carbohydrate (304 participants) diet. Their weight change was measured at 12 months.

The study also tested whether three single-nucleotide polymorphism multilocus genotype responsiveness patterns or insulin secretion (INS-30; blood concentration of insulin 30 minutes after a glucose challenge) were associated with weight loss.

The diet was delivered by health educators, with sessions focusing on ways to achieve the lowest fat or carbohydrate intake that could be maintained long-term and emphasized diet quality.

“Among 609 participants randomized (mean age, 40 [SD, 7] years; 57% women; mean body mass index, 33 [SD, 3]; 244 [40%] had a low-fat genotype; 180 [30%] had a low-carbohydrate genotype; mean baseline INS-30, 93 μIU/mL), 481 (79%) completed the trial,” the authors wrote.

“In the HLF vs HLC diets, respectively, the mean 12-month macronutrient distributions were 48% vs 30% for carbohydrates, 29% vs 45% for fat, and 21% vs 23% for protein.

“Weight change at 12 months was −5.3 kg for the HLF diet vs −6.0 kg for the HLC diet (mean between-group difference, 0.7 kg [95% CI, −0.2 to 1.6 kg]).

“There was no significant diet-genotype pattern interaction (P = .20) or diet-insulin secretion (INS-30) interaction (P = .47) with 12-month weight loss. There were 18 adverse events or serious adverse events that were evenly distributed across the two diet groups.”

The authors concluded that in the context of these two common approaches to weight loss, neither of the two hypothesised predisposing factors was helpful in identifying which diet was best for which patient.

High-profile nutritionist Dr Rosemary Stanton said this was an “excellent” study.

“Its major finding appears to be related to several facts: all participants were asked to maximise vegetables and minimise added foods with sugars, refined flour products or trans fats. They were also advised to choose high quality foods that were nutrient-dense and minimally processed, and, where possible, prepared at home,” she said.
“Under these circumstances and with professional help and support to choose quality foods, the study shows that the macronutrient content of the diet does not really matter.
“Some previous studies that have damned carbohydrates have not taken note of the foods that supplied it.

“For example, lentils and lollies are both ‘carbs’ but one is a nutrient-dense high quality food while the other is junk. Simply calling them ‘carbs’ does not provide this vital distinction.”

And Professor Lennert Veerman from the School of Medicine at Griffith University said that the results suggests that “there is probably not such a thing as a diet that is right for your particular genetic make-up”.

“The fact that the diets led to similar weight loss confirms earlier research that suggested that it doesn’t much matter what diet you follow (low fat, low carb, etc.) – they all work. It all comes down to consuming fewer calories.

“While most diets work, the real challenge is sticking with them. The evidence suggest that after a promising start of the diet, people regain the weight they lost.

“Instead of ‘going on a diet’, it would be better to find new, healthier habits. But for that to work, most people will need an environment that encourages healthy eating, rather than one that is full of heavily advertised, convenient and affordable junk food.”

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