This article is an excerpt from the Shortform book guide to "Fast. Feast. Repeat." by Gin Stephens. Shortform has the world's best summaries and analyses of books you should be reading.
Like this article? Sign up for a free trial here .
Does intermittent fasting help with fat loss? How does fasting compare to dieting in terms of weight loss?
Many people resort to dieting by restricting their calories in an effort to lose weight. But dieting is not an enduring solution. As many dieters can attest, the excess weight often comes back once the diet is over. According to Gin Stephens, intermittent fasting can help you lose weight and keep it off long-term.
Here’s why fasting is a better approach to weight loss than traditional dieting, according to Stephens.
How the Body Stores and Uses Energy
Stephens explains that when we eat, our blood glucose (blood sugar) levels increase. In response, our bodies release insulin, a hormone that stores excess glucose in the liver and muscles as glycogen. If any blood glucose remains after this step, insulin converts it into fat and stores it away.
By storing this glucose-based energy, insulin lowers your blood glucose. When your blood sugar runs out and you need energy, the pancreas signals for your liver to release some of its stored glycogen to use as energy. When those glycogen stores run out, you enter the fasted state.
In the fasted state, your body converts your fat stores into ketones, a fat-based energy source. Put another way, you’ll burn your fat as fuel (a state called ketosis). We evolved to burn fat for energy when food was scarce, so you’ll do so only after depleting your blood glucose and glycogen stores.
Dieting Doesn’t Facilitate Sustainable Fat Loss
Stephens explains that diets don’t lower insulin levels enough to deplete your glycogen stores and start burning fat. This is because diets work on the logic of “calories in, calories out”—that is, eat less than you need and you’ll lose weight.
While dieting or eating less works temporarily, it also causes metabolic adaptation, a scenario wherein your metabolism slows down to deal with perceived starvation. It works like this: When you eat fewer calories than you need to maintain your weight, your body thinks you’re starving. Then, Stephens says, it makes three changes to handle the situation:
- The hunger hormone, ghrelin, increases. This makes you want to eat more.
- The satiety hormone, leptin, decreases. This makes you less satisfied, so you’ll want to stuff yourself.
- Your metabolism slows down. This lowers your energy levels and slows you down, so that you can “survive” until food becomes available again.
Diet for long enough, and your metabolism settles in at that slower pace—that’s the “adaptation” in metabolic adaptation. Then, you’ll need to eat even less to continue losing weight, since you aren’t burning as much energy—creating a downward spiral of hunger and slowing metabolism.
Fasting Promotes Effective Fat Loss
Dieting typically doesn’t involve fasting, so when you diet, you never use the built-in fat burning mechanism your body already has. Here’s how to access it.
Since our bodies are used to overeating, we need to teach them to access our fat stores again. According to Stephens, when you start fasting, your body won’t yet know how to burn fat and will instead slow your metabolism to save energy until you can eat again.
Since insulin releases when you eat, fasting allows insulin levels to decrease. Then you can use up your liver’s stores of glycogen and begin to access your fat stores. If you fast often enough, your body will “remember” it has fat stores to burn for energy.
According to Gin Stephens, intermittent fasting promotes sustainable fat loss. Each time you burn fat for fuel, you’ll lose some weight—and with fasting, you’ll also eat enough each day, so you won’t cause your metabolism to slow down.
———End of Preview———
Like what you just read? Read the rest of the world's best book summary and analysis of Gin Stephens's "Fast. Feast. Repeat." at Shortform .
Here's what you'll find in our full Fast. Feast. Repeat. summary :
- How intermittent fasting can help you lose weight, feel better, fight disease, and live longer
- An explanation of the cutting-edge science that supports fasting
- How to follow a four-week quickstart program to adapt to this new lifestyle
