A major diet study showed that people who reduce their refined carbohydrate intake without reducing their fat intake lose more weight and have a lower cardiovascular risk than people on on a low fat diet


Quick: What’s worse for the heart – a double cheeseburger or the coke to wash it down? The cheeseburger, most people would say. And that is actually the “informed opinion” on which most dietary recommendations are based.

A recent article in the Annals of Internal Medicine is likely to debunk such mistaken beliefs. It reports on a major diet study showing that people who reduce their refined carbohydrate intake without reducing their fat intake lose more weight and have a lower cardiovascular risk than people on on a low fat diet.

First, how did we come to believe that fats, especially saturated fats, are “bad for you”? Actually, a pretty familiar story. Biochemical research showed that cholesterol is synthesized from lipids. Other studies showed that cholesterol is involved in atherosclerosis. But does that mean that a high fat diet causes cardiovascular disease? If A leads to B, and B leads to C, does it mean that A necessarily leads to C? As tempting as it is to make this connection—it ain’t necessarily so.

The new study included a racially diverse group of 150 men and women who were assigned to follow diets for one year that limited either the amount of carbs or fat that they could eat, but not overall calories. This design is remarkable; unlike highly controlled diet studies that bear little resemblance to real life, this one allowed the subjects to eat foods that real people eat in real life.

The high fat/low carb diet might consist of eggs for breakfast, tuna salad for lunch, and some kind of protein for dinner—like red meat, chicken, fish, pork or tofu—along with vegetables. Low-carb participants were encouraged to cook with olive and canola oils, but butter was allowed, too. Over all, they took in a little more than 13 percent of their daily calories from saturated fat, more than double the 5 to 6 percent limit recommended by the American Heart Association. The majority of their fat intake, however, was unsaturated fats.

The low-fat group included more grains, cereals and starches in their diet. They reduced their total fat intake to less than 30 percent of their daily calories, which is in line with the federal government’s dietary guidelines. The other group increased their total fat intake to more than 40 percent of daily calories.

Both groups were encouraged to eat vegetables, and the low-carbohydrate group was told that eating some beans and fresh fruit was fine as well.

 

And the results?

By the end of the yearlong trial, people in the low-carbohydrate group had lost about eight pounds more on average than those in the low-fat group. They had significantly greater reductions in body fat than the low-fat group, and improvements in lean muscle mass—even though neither group changed their levels of physical activity.

The low-carbohydrate group had a marked reduction in the markers of inflammation and triglycerides. Their HDL, the so-called good cholesterol, rose more sharply than it did for people in the low-fat group.

Blood pressure, total cholesterol and LDL, the so-called bad cholesterol, stayed about the same for people in each group.

Nonetheless, those on the low-carbohydrate diet ultimately did so well that they managed to lower their Framingham risk scores, which calculate the likelihood of a heart attack within the next 10 years. The low-fat group on average had no improvement in their scores.

 

So what’s the bottom line?

In a recent post on nutritional studies we wrote that our metabolism is enormously complex and that purporting to isolate one or more components of the diet as panaceas or culprits, whichever the case may be, are exercises in futility. All the biggest computers in the world, combined, cannot begin to comprehensively model our metabolism. So why make things so difficult? Just keep it simple:  eat a well-balanced healthy diet.

One diet that is the favorite of many nutritionists and researchers is the Mediterranean Diet. It contains plenty of fresh produce, olive oil, nuts, beans and seafood. It also includes moderate amounts of poultry, eggs, cheese and yogurt, and some meat. It’s “good for you”, and delicious to boot. As the commercial promised, “you’ll like the way you look; I guarantee it.”


Featured Photo Credit: Simon Doggett

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