How restricting calories affects your metabolism

The metabolic slow-down caused by caloric restriction has been scientifically proven for decades, yet nutritional authorities continue to recommend this strategy for weight loss.

The advice goes something like cut your caloric intake by 500 calories per day and lose 1 pound per week. But this affects the body’s energy levels needed maintain basic metabolic functions. In other words long-term caloric restriction causes the body’s basal metabolism– the energy expenditure required to remain alive at rest–to drop.

As far back as 1969, a study was conducted in which obese patients were put on a rich, 3,500 calorie diet for one week. Then they drastically reduced their calories to 450 per day. During this time basal metabolic rate declined by 15%, and as a result after three weeks on the calorie restricted diet, body weight declined by just 6%.

As metabolism drops weight loss plateaus, as the body slows down in order to match the lowered caloric intake.

What science today shows more and more convincingly–though it is still a topic of investigation–is that calorie restricted diets only work in short term spurts, before basal metabolism falls. That’s where intermittent fasting comes in.

There are many ways to fast intermittently, for instance eating normally for 5 or 6 days a week and then consuming a few hundred calories one or two days a week to allow the body to tap into its fat stores for energy. When the body must tap into burning fat for fuel, basal metabolism does not decrease, actually it increases a bit. This method also increases the body’s sensitivity to insulin which is crucial for burning fat.

If intermittent fasting is not for you, strength training, which works the muscles hard and increases insulin sensitivity, also helps the body burn fat more effectively. Strength training revs up the metabolism and allows the body to burn more calories while at rest. The combination of strength training and intermittent fasting can be a powerful way to alter your body.

Of course the composition of the diet matters greatly in all these situations. These techniques must be accompanied by a lifestyle change, not a temporary fad diet, where whole, unprocessed foods including lots of vegetables, are consumed for the most part.

Science is also showing more and more that the quality of the diet, not the number of calories, is much more important for our weight. If you’re eating nutrient rich foods, and stopping to eat when you’re full, there’s no need to count every last calorie.