Study: Low-Fat is More Effective Than Low-Carb for Weight Loss
A new study has been published in the peer-reviewed journal Cell Metabolism with the title: Calorie for Calorie, Dietary Fat Restriction Results in More Body Fat Loss than Carbohydrate Restriction in People with Obesity.
It was a relatively small study conducted by The National Institute of Health, with only 19 participants, but it was very tightly controlled – the participants all had to remain in the laboratory for 2 weeks while being closely monitored. Participants lost an average of 3.1 ounces of fat per day while on the low-fat diet for six days. When put on the low-carb diet, participants lost an average of 1.9 ounces of fat per day in the same amount of time.
From the paper’s summary:
Subjects received both isocaloric diets in random order during each of two inpatient stays. Body fat loss was calculated as the difference between daily fat intake and net fat oxidation measured while residing in a metabolic chamber. Whereas carbohydrate restriction led to sustained increases in fat oxidation and loss of 53 ± 6 g/day of body fat, fat oxidation was unchanged by fat restriction, leading to 89 ± 6 g/day of fat loss, and was significantly greater than carbohydrate restriction (p = 0.002).
By no means is this the end of the low-carb vs low-fat debate. Cursory searches online point to several studies which show that low-carb diets offer the best weigh-loss results for some people. But this study did further contribute to the ever-growing body of evidence that its not necessarily what types of food you eat (fats vs carbs) but rather that weight loss, ultimately, comes down to reducing the number of calories consumed.
“But this study did further contribute to the ever-growing body of evidence that its not necessarily what types of food you eat (fats vs carbs) but rather that weight loss, ultimately, comes down to reducing the number of calories consumed.”
Yeah, if by “contribute” you mean undermine. Both diets had the same number of calories (“isocaloric diets”), but the low-fat diet had a 68% higher rate of fat loss, at least for six days.
You left out the last sentence of the summary that says, “Mathematical model simulations agreed with these data, but predicted that the body acts to minimize body fat differences with prolonged isocaloric diets varying in carbohydrate and fat.”
So in the long run the fat loss on different isocaloric diets may be the same, but that’s just a prediction, not an observation of this study.
Two weeks.
It’s not just a small study, it’s a very short study.
There is one major reason why it’s important. In much longer studies, low carb high fat diets have been shown to be at least as effective for weight loss as low fat diets, but the diets compared are almost always different in another way. The low fat ones are calorie counted like this one, while the low carb is “ad libitum”, i.e. people eat as much as they feel they need to, with only sometimes a general guideline to eat less.
What do you think is more sustainable? I’ve lost weight on a calorie counted diet. It works. Then you hit a drop in motivation and you gain it back, because it requires a constant struggle. No such issue with low carb, I keep on truckin’ even when I’m depressed.
There is also the issue of lean mass loss. Surveys pitting low carb and low fat show the latter preserves muscle mass. Add to that that outside the context of clinical trials, it’s much easier to eat sufficient proteins on a low carb diet. In fact it’s actually hard not to overshoot on proteins, while it’s the opposite on a low fat diet.
Compare the protein content of a typical low fat high protein staple, lentils (70g for 30g of proteins) to that of cheese (50g of fat for 50g of proteins) or even bacon (55g of fat for 45g of proteins). In terms of calories, it’s closer because fat is more calorie-dense, but lentils are exceptionally high in proteins. Nothing comes close.