Intermittent fasting is currently one of the hottest health and fitness trends. So is it backed by scientific fact, or is it just another fad? Some argue it only works because it reduces weekly caloric intake, which it does. However, studies suggest that fasting also influences hormones that make it easier to lose the weight, and keep it off.
Intermittent fasting (IF) involves scheduled windows of going without food to train the body to burn fat instead of sugar. Provided you don’t overeat during non-fasting periods, IF reduces overall caloric intake, which should lead to weight loss. It’s important to note that this is not the only way fasting induces weight loss. Several things happen to your body on a cellular and hormonal level when you fast. It doesn’t just help you eat fewer calories; it also helps you burn more calories and stored fat!
A lack of available glucose during fasting shifts the body into ketosis, or burning stored fat for fuel. This shift is largely due to changes in two particular hormones: insulin and glucagon. Fasting decreases levels of the fat-storing hormone insulin, while increasing levels of the fat-burning hormoneglucagon. Insulin’s job is to lower your blood sugar by shuttling glucose into cells to be burned for energy. Insulin blocks access to your body’s fat stores because your body will preferentially burn sugar over fat (metabolically, it’s an easier process). High insulin also signals the body to store excess glucose as fat. Glucagon’s job is to raise your blood sugar by releasing stored glucose to be burned for energy. It also causes lipolysis, the process of releasing and burning stored fat. Studies have consistently backed the effects of insulin and glucagon on fat loss. Animals that receive insulin gain body fat and have higher appetites. Animals that receive glucagon lose body fat and eat less. The bottom line: Insulin promotes fat storage and slows weight loss by blocking access to your fat stores. Glucagon breaks down stored body fat and burns it for energy.
There are a number of popular approaches to intermittent fasting, some of which may be too extreme. We prefer the following, especially for female clients who do not tolerate fasting the same way males do:
- The Overnight Fast: this is the simplest method and most appropriate for the average person. It involves fasting for 12 hours overnight to help reset insulin levels and allow the body to focus on repair versus digestion.
- The 16/8 method: also known as the Leangains protocol, it involves restricting your daily eating period to an 8 hour window (for example 10 am-6pm) and fasting for 16 hours between windows. This method is not appropriate for women with hormone, thyroid, or blood sugar imbalances.
Although weight loss is the primary reason most people adopt an intermittent fasting protocol, fasting offers several additional health benefits. Fasting has also been shown to:
- Boost human growth hormone (HGH): when you fast, levels of HGH can increase up to 5-fold. HGH may help increase lean muscle mass, regulate other important hormones, and combat cellular aging.
- Improve insulin sensitivity: fasting improves cellular response to insulin. This lowers blood sugar levels and improves the body’s ability to burn fat, decreasing the risk of obesity and Type 2 diabetes.
- Initiate cellular repair: when your body isn’t so focused on digestion, it has time and energy to devote to cleansing and repair on a cellular level. Fasting increases a process called autophagy, the process of breaking down and recycling old cellular parts.
If done properly, intermittent fasting can be a great addition to a healthy diet and exercise regimen. It’s easy to implement and doesn’t require tedious calorie counting or restricting entire food groups. Fasting also increases the fat-burning hormone glucagon, while decreasing the fat-storage hormone insulin to help accelerate your fat loss!