Fasting for Fast Fitness

The latest big fad, spurned by a 2012 book, is intermittent fasting, meaning fasting on alternate days. But a recent review article indicates that fasting may actually offer more than initially thought.

Scientists and doctors have long known that eating too few calories can actually interfere with losing weight. When the body doesn’t have enough energy, it can go into a type of starvation mode where it stores as much energy as possible as fat.

The reasons for this stem from how our bodies evolved. When the body is starving, it uses up energy stored in fat first, but then starts using energy stored in muscle proteins. But losing muscle is a last resort. So in order to avoid losing muscle mass while starving, the body first tries to reduce its basal metabolic rate.

In normal people, the body burns close to 1500 calories a day (depending on your age and sex). This is the regular basal metabolic rate, or how much energy is used during normal activities. When the basal metabolic rate drops, the amount of calories burned during rest drop as well.

The other effect of taking in too few calories: less energy for exercise and activity. Between the drop in resting metabolism and being to tired to work out, starving yourself can easily keep you from losing weight.

But this is where intermittent fasting comes in. Rather than reducing calories daily, which can be hard for people to keep track of, this new diet just asks that you reduce your caloric intake to 500-600 for two days a week, and eat within your normal caloric range on all the other days, about 1800-2500 (calculate your range).

By spacing out your fasting this way, you can avoid the trap of sending your body into starvation mode. You can also help your metabolism work more efficiently. Unlike previous methods, which tried intermittent starving, consuming zero calories on alternate days, intermittent fasting doesn’t trigger the body’s starvation mode.

The authors of the review indicate that this type of caloric restriction could help treat diabetes, aid in weight loss, and reduce cardiovascular disease. The implications are especially relevant for obese and morbidly obese individuals who may have no options but risky bariatric surgery. One study the authors cited suggested that intermittent fasting could be as effective as surgery in improving health outcomes.