Intermittent fasting can provide flexibility, convenience, affordability and simplicity to any diet if implemented correctly, according to a presentation at the Obesity Medicine Association Spring Conference.

During his presentation, Jason Fung, MD, a nephrologist and founder of The Fasting Method, discusses how to approach intermittent fasting with a hormonal model of obesity instead of the calorie model, which treats all calories as equally fattening.

According to the Cleveland Clinic, intermittent fasting is a meal-timing schedule that involves alternating between cycles of eating and fasting. There are several types of intermittent fasting. Fung discussed the 16/8 time-restricted eating method, in which patients have a 16-hour window of fasting and an 8-hour window to eat daily.

The hormonal model, or the carbohydrate insulin model, asserts that food contains both energy and information, according to Fung.

“The hormonal response to foods is quite different,” he said.

For example, eating cookies can result in an insulin spike, but broccoli will not. The instructions sent to the body by the foods are different since they have different hormonal profiles.

This aspect of food consumption complicates the calories in/calories out approach to weight loss since there is a third component: body fat. Fung uses an equation (body fat = calories in calories out) to illustrate the need to balance each component.

“If you simply eat fewer calories, that does not necessarily mean that your body fat will go down because there is a third variable (calories out) that could change in order to balance the equation,” he said.

Research indicates that any reduction in calories is met with a similar reduction in metabolic rate, which will minimize fat loss.

“This is a natural evolutionary response to a reduction in calories in; you want to defend your body weight,” Fung said.

A similar reaction to metabolic rate occurs with exercise when a person does not replenish their calorie expenditure.

“There comes a point where the more exercise you do, you don’t get any further increase in total calories that you use in a day,” he said. “What happens is that the extra energy that you use simply is taken out because your metabolic rate goes down by an equal amount.”

Both the total amount of calories a person consumes and their hormones are important. Hormones control hunger, satiety and the metabolic rate, according to Fung. This is the root cause of weight gain and addressing this can benefit weight loss.

Fasting is a way for a person to consume fewer calories while fixing the hormonal environment of their body to be conducive to weight loss, according to Fung. When insulin falls during periods of fasting, the body can take energy out of its storage (fat).

“Hunger tends to go down with fasting, which is what we see clinically as well,” Fung said.

After establishing the habit of intermittent fasting, feelings of hunger will diminish, the body will adapt to a new baseline and calories will be pulled from body stores.

There is a concern for disordered eating with intermittent fasting. However, previous studies have indicated a correlation, not a causation.

“It doesn’t mean the behavior causes the disease,” Fung said.

Overall, fasting reduces hunger and the metabolic rate and provides consistency and structure to an eating plan. It may also be easier for people to follow since they are counting hours of the day instead of calories. However, patients should never be advised to eat whatever they want and however much they want during non-fasting hours, according to Fung. Fasting does not dictate what should be eaten, only when eating should occur, which can be paused and restarted around life events.

The intermittent fasting method has been used for centuries and is “actually the simplest thing,” Fung said.

“If you want to lose weight, just don’t eat all the time,” he said.