Researchers love twin experiments because health is so heavily determined by genetics. However, nutrition and exercise also significantly affect health, which is why this recent month-long twin experiment in Britain is so interesting.

Two brothers, twins Chris and Xand, who are both physicians with similar lifestyles and identical fitness regimens, decided to test which nutrient was worse for you: Sugar or fat. The no-sugar, or ultra-low-fat diets are fairly common approaches to weight loss, but it turns out neither are the best method for pursuing a healthy lifestyle. Well I could have told them that!

Low-Fat

Chris adopted the low-fat diet, allocating the bare minimum of 2 percent of his daily total intake to fat. Essentially, he mimicked the “Non-Fat” craze that took over much of the diet market in the 1990’s. Interestingly, in the late 1980’s, two major reports came out identifying dietary fat as the most important change to improving health, which resulted in food manufacturers substituting sugar for fat (ie. Snackwell cookies).

As many 90’s dieters (and Chris) discovered, severely reducing fat does not lead to losing weight. The Low-fat dieting twin experienced constant feelings of hunger, which made him eat more in calories despite the low fat count.

Sugar-Free

Xand, the other twin, went for a high protein diet that eliminated carbohydrates – not just table sugar, but also flour and fruit which convert to sugar – similar to the Atkins diet. When the Dr. Atkins Diet Revolution was first published in 1972, the President of the American College of Nutrition was quoted as saying “Of all the bizarre diets that have been proposed in the last 50 years, this is the most dangerous to the public if followed for any length of time.”

Xand discovered that eliminating all sugar had some nasty side effects, including less energy and stamina, bad breath, constipation, and fatigue. He did lose more weight (a total of 9 pounds in the course of the month), but he said the low-carb, high-protein diet caused his body to go into ketosis (the body burns fat, but doesn’t provide enough glucose to the brain). Ketosis can also lead to kidney failure.

And The Winner Is?

So which is better: No sugar, or Low-fat? It turns out, both are “pretty miserable” in the words of the brothers.

Their conclusion, according to Chris, was “We should not vilify a single nutrient.” The twin doctors reportedly decided that it’s the combination of sugar and fat found in many processed foods that is the real source of diet-related problems. They recommend watching calories and portion size while eating mostly whole foods. The experiment might be news, but the conclusion sounds like common sense to me!