A study comparing low-fat and low-carb diets may have revealed the real best diet for your body and brain

  • A large study published this week suggested that neither a low-fat diet nor a low-carb diet is superior for weight loss; both plans work.
  • Neither diet was strict when it came to fat or carbohydrates.
  • More important, participants in both the low-carb group and the low-fat group were instructed to eat lots of vegetables and protein while limiting their intake of added sugar and refined carbs.

A robust study published this week pitted two popular diets against each other and came away with a surprising finding: Neither a low-fat diet nor a low-carb diet is superior for weight loss.

People assigned randomly to either plan lost weight at about the same pace and kept it off for roughly the same amount of time.

At first glance, that finding seems to fly in the face of recent scientific wisdom on diet and health, which has begun to recommend welcoming fatty foods like butter and eggs back into our diets and curbing our intake of sugar and carbohydrates such as rice and bread.

But not so fast. In reality, the study did not compare a truly low-carb diet against a low-fat one. The people in the low-carb group were actually eating a relatively high number of carbs. They were nowhere near the next-to-nothing carb counts that people on regimens like the keto diet achieve.

More important, all the participants in the yearlong study – regardless of which group they were in – were put on a healthy eating plan that diverges dramatically from what most Americans eat.

All the participants were told to ramp up their intake of vegetables and slash their consumption of added sugars and refined grains – two nuggets of nutritional wisdom that the vast majority of Americans have yet to incorporate into their daily lives.

People on both diets lost the same amount of weight, but neither was truly ‘low-fat’ or ‘low-carb’

Woman eatingShutterstock

The recent study was published Tuesday in the Journal of the American Medical Association. The researchers randomly assigned 609 nondiabetic overweight adults age 18 to 50 to the low-fat or low-carb diet.

At the end of the study, people in both groups were found to have lost about the same amount of weight: 13 pounds, on average.

But precise rules regulating the quantities off carbs or fat the participants ate were put in place for only the first two weeks of the study, making it hard to measure actual quantities of carbs or fat consumed.

Plus, the participants were given other guidance on what to eat that could have played a large role in the outcomes the researchers observed.

Avoiding refined carbs and sugar may be key for overall health

Erin Brodwin / Business Insider

All the participants were given two additional instructions on how to eat. First, they were told to “maximise vegetable intake” by eating lots more foods like bell peppers, kale, and collard greens, all of which have been linked to positive outcomes like weight loss and a reduced risk of disease.

Second, they were instructed to curb their intake of added sugars and refined flours, ingredients that studies have increasingly tied to a variety of negative health outcomes, including weight gain and diabetes. These ingredients make up the vast majority of carbs in American diets. Beyond obvious carb-heavy items like bagels and rice, sugar and carbs lurk in an array of seemingly healthy foods like salad dressings, yogurt, sauces, and supposedly “light” ice creams.

A growing body of evidence suggests that eating fewer refined carbs and more vegetables is helpful not just for losing weight and keeping it off but also for reducing your risk of several major diseases, including heart disease, diabetes, and some types of cancer.

“Added sugars and refined grains are consistently singled out by health professionals from across all sectors, and by proponents of every diet type I can think of as being the lowest quality contributors to the human diet, and the first place to go when eliminating calories from daily intake,” Christopher Gardner, a professor of Medicine at Stanford University and the lead author on the latest paper, told Business Insider.

Participants in both studies ended up eating roughly the same amount of protein each day. That’s unsurprising, given that protein-rich foods like eggs, fish, avocados, and beans fill us up and keep us full, making us less likely to over-indulge on such items.

The bigger takeaway from the study, then, seems to be that any eating program that curbs your intake of refined carbs and added sugars while prioritising vegetables, proteins, and whole grains can help you lose weight.

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