The Science - Intermittent Fasting

The Trim® Carb Revolution™ program uses intermittent fasting (IF), which is currently one of the world’s most popular health and fitness trends. Many studies show that fasting can have powerful positive effects on your body and brain. Intermittent fasting is not a diet, but rather a way of scheduling your meals so that you get the most out of your food. An intermittent fasting period is most easily determined as the time from your last meal at night until your first meal the next day. The fasting period usually varies from 12-16 hours and may be easiest to start with 12 hours. Start with eating your last meal by 10 p.m., and then having first meal around 10 a.m., for a 12-hour fasting period. You can adjust the hours gradually to hit the 16 hour fast.

Research supports that fasting can increase fat oxidation, reduce body weight, and accelerate fat loss. These benefits are a result of the fasting period causing improved insulin sensitivity, improved hormone production and balance, nerve regeneration, and the benefits of reaching low-level ketosis. During periods of fasting your body’s level of blood glucose significantly decreases, which lowers insulin release, resulting in increased fatty acid oxidation and fat burning. When you maintain adequate protein and fat intake there is no muscle loss and you can achieve a healthy lean body mass.

In a recent study in Cell Metabolism, periodic fasting was linked to lower risks of heart disease, diabetes, cancer, and aging. When performing effective fasting there is cell turnover and clean up of bad or damaged cellular tissue (autophagy), which in turn initiates stem cell activity starting a regeneration process that gives rise to new, younger cells. Other studies have shown that intermittent fasting may decrease low-density lipoprotein (LDL) or “bad” cholesterol, reduce inflammation and improve insulin resistance.

Intermittent fasting has several effects on hormones that demonstrate the benefits of adopting this program over the long-term. By discontinuing eating by 8-10 p.m. in combination with skipping breakfast, you create a 12-16 hour fasting period that helps reset your hormones and pushes the body to use fat as its primary fuel. The old theory is to eat a high-carbohydrate breakfast; however, that causes insulin and glucose levels to spike- essentially shutting off fat-burning for several hours and driving unused calories into fat stores. These high spikes of insulin and glucose lead to large drops in glucose a few hours later, which will also trigger hunger. Fasting does the opposite by controlling hunger and maximizing fat burning through the help of these following hormone changes:

  • Insulin: In the fasted state, insulin is low, while glucagon and growth hormone are elevated. The body starts mobilizing stored body fat from your fat cells and burning this fat for energy instead of glucose.
  • Human Growth Hormone: Fasting can also have a strong impact on growth hormone (GH) secretion. Growth hormone is generally highly secreted when we sleep and decreases when we have breakfast, however levels of GH continue to rise if you prolong the overnight fast to optimize fat burning and reduce inflammation.
  • Leptin: Fasting helps regulate leptin, the “satiety hormone”. Leptin levels fall during fasting and then return to normal after eating, alerting you to stop eating. It also helps overcome leptin resistance that occurs with the accumulation of fat.
  • Ghrelin: Fasting helps normalize ghrelin, the “hunger hormone” by acting as a natural appetite suppressant. When fasting, ghrelin levels increase which also stimulates growth hormone release. This in combination with an increase in good fats can really curb food cravings.
  • Cortisol: The hormone cortisol plays a large role in fat burning and is naturally highest in the morning. Thus, in order to maximize this natural fat burning window, it is an important to refrain from eating early morning meals.
  • Testosterone: Fasting can increase luteinizing hormone (LH), which is a precursor to testosterone synthesis. Research also supports that fasting can directly increase testosterone levels in men and women.