Being fit and healthy is a very important issue for people worldwide, just considering that 45 million Americans go on a diet every year and spend billions on weight-loss products (yet more than a third remain obese).

The diet issue has always been confusing because of the different theories, but it seems that after 12 year of researches, the scientific true is revealed.

A new diet lab rigorously enforced either a low-carbohydrate or low-fat diet for 19 obese men and women over six days. The six-day low-carb diet led to more weight loss than a low-fat diet, but the low-fat diet led to more fat loss.

The study, leaded by Kevin Hall, PhD–a physicist turned metabolism researcher at the National Institute of Diabetes and Digestive and Kidney Diseases- confined 19 obese adults (9 men, 10 women) to a "metabolic ward", or diet lab, for two two-week periods while on low-fat or low-carb diets. While in the diet labs, researchers monitored and restricted their diets, energy intake and expenditure, and used a host of biological measures to establish whether they were burning fat or carbohydrates as their source of energy.

Each person spent five days in the diet lab on an energy-balanced diet (50% carbohydrate, 35% fat, 15% protein) before being randomly assigned to a diet that slashed their calorie intake by 30% (around 800 calories a day lower) for a further six days. This was achieved either through a 60% reduction in carbs (low-carb diet) or an 85% reduction in fat (low-fat diet).

After a two- to four-week washout period where they could eat what they liked, volunteers were readmitted to try the other diet. This repeated the five-day balanced diet followed by the alternate six-day low-fat or low-carb diet.

Both diets led to weight loss over the six days, but those on the low-carb diet lost significantly more. After six days the low-carb group had lost about 1.85kg on average compared with around 1.3kg on the low-fat diet, around a half kilo difference in just six days.

The low-carb diet led to significant changes in metabolic fuel selection. Insulin levels dropped, which lowered carbohydrate burning by around 500 calories a day and increased fat burning by around 400 calories a day.

In other words, the low-fat diet resulted in a greater body fat loss compared with the low-carb diet, despite being equivalent in calories.

Researches are very optimistic about this study, saying: "Fat loss is a more important goal than weight loss in the treatment of obesity and that outside of the highly controlled diet lab".

More specifically, this diet lab study showed that a six-day low-carbohydrate diet affects a person's metabolism far more than a low-fat diet. The low-carb diet led to more fat burning and overall energy expenditure via lower insulin levels, whereas the low-fat diet didn't alter fat or carb-burning proportions, but led to more fat loss.

Even though those results are very optimistic, we shouldn’t forget the four simple words of advice – eat less, exercise more, which seems to be very effective.



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