People have been talking about intermittent fasting for years, claiming it is the best way to boost your metabolism and lose weight. Does the diet actually hold up to the hype?

What Is Intermittent Fasting?

In simplest terms, fasting is a period of time when you are not putting calories into your body. Fasting is part of the human experience. Every time you go to sleep, you fast. Between each meal or snack, you fast.

Technically speaking, intermittent fasting is how you live your life each and every day. The difference when it comes to the dietary trend is that you stretch your period of fasting into longer intervals.

What makes intermittent fasting more appealing than other diets is that you adjust when you eat, not what you eat.

How Does the Diet Work?

We need energy every minute of every day. Even when we are sleeping, we can burn as much as 0.42 calories per pound per hour!

Calories are our energy currency. These calories come from the food we eat or at least they start out that way. We generally eat more calories than our body needs in any given moment. The body has processes in place that take those extra calories and store them for times we need a boost of energy.

• The Fed State: When we eat, there is lots of glucose in the bloodstream. This causes insulin levels to rise. The insulin then takes any extra glucose, links it into chains, and stores it as glycogen in the liver. The problem is that the liver can only store so much glycogen. Once it reaches capacity, it starts to turn the extra glucose into fat. Some of that fat will stay in the liver and some of that fat will move to other parts of the body.
• The Fasting State: When blood sugar levels go down, insulin levels decrease. Instead of building glycogen, the liver starts to break it down into glucose. There is usually enough glycogen to last 24 to 36 hours on a regular day but only a few hours if someone performs vigorous exercise. Once glycogen stores are depleted, the body turns to other energy sources. It starts to break down fat and in later stages muscle. This allows fatty acids and amino acids to be used as alternative sources of energy.

Understanding how metabolism works, it is easy to see how intermittent fasting promotes weight loss. In the fasting state, the body is nudged into breaking down fat for energy.

Intermittent Fasting Is Not Starvation

Many people are afraid that intermittent fasting will put them into starvation mode. The fear is that their metabolism will slow down and it will be harder to lose weight. The truth of the matter is you are unlikely to fast long enough for that to happen. A day or two of straight fasting is simply not going to do it.

Starvation is essentially a state of malnutrition when the body is missing key nutrients to function properly. The body goes through three phases as it adapts to long-term calorie and nutrient restriction.

• Phase 1: Glucose as the major source of energy (breakdown of glycogen)
• Phase 2: Fat as the major source of energy (breakdown of fat)
• Phase 3: Protein as the major source of energy (breakdown of muscle)

In starvation, your glycogen stores are used up. Your body then relies on the breakdown of fat and to a lesser extent muscle over several weeks before it turns more heavily to breaking down muscle. At that point, your organs could be damaged and you could face a life-threatening situation.

Interestingly, although your metabolism does slow down in starvation, studies show that your metabolism actually gets a boost with short-term fasting. That is another benefit to using intermittent fasting for weight loss.

The Verdict

In theory, intermittent fasting as a diet shows a lot of promise. The metabolism gets a boost and it is easier to burn fat. But is the diet for everyone? Not necessarily. It depends how you do it, not to mention that women respond differently to the diet than men.