The Theory Behind Intermittent Fasting: Returning to Natural Eating

What is the theory behind intermittent fasting? Where does the idea come from?

The theory behind intermittent fasting is that our early ancestors ate with fasting cycles, and that our shift into eating three meals a day goes against our natural instincts and needs. A look at this backstory gives insight into when intermittent fasting might be helpful.

Learn more about where the idea of intermittent fasting came from in recent history.

Intermittent Fasting Returns Us to Our Natural Way of Eating

In Fast This Way, Dave Asprey explains the theory behind intermittent fasting. He writes that our modern eating habits differ dramatically from our ancestors’. Most of us believe we need food more than we really do, and thus we eat three meals a day—or more. Asprey argues that this pattern of eating isn’t driven by our natural needs but instead is a product of the Industrial Revolution, when people adjusted their eating habits to fit factory and train schedules.

(Shortform note: The American norm of eating three meals a day may date back further than Asprey suggests, with some experts tracing it back to the colonization of America by European settlers. The Native Americans had a flexible and seasonal approach to eating, which the Europeans saw as “uncivilized” and inferior. So, to distinguish themselves as more cultured and civilized, the Europeans adopted a more rigid eating schedule that the Industrial Revolution—and the lifestyle changes it brought about—later reinforced. Thus, experts argue that this meal regimen not only has little basis in our body’s metabolic needs but may also have emerged as a result of racial prejudice.)

Asprey argues that by intermittent fasting (alternating between specific windows of eating and not eating), you can eat according to your body’s true needs—you’re biologically programmed to get energy from food and then allow your body to rest and heal. Our ancestors used to eat in this way as they regularly cycled between feast and famine depending on the availability of food.

(Shortform note: Some experts argue that just because our ancestors ate in a certain way, it doesn’t mean it’s good or healthy for us today. They point out that people had much shorter lifespans back then and often suffered from nutrient deficiencies. They also counter the assumption that our bodies haven’t evolved to handle modern food, arguing that evolution occurs quicker than we often think. Because of this, they question whether we (who live longer and have more control over our eating) would benefit from adopting our ancestors’ diet. In other words, while fasting may have its benefits, it’s not necessarily because it mirrors our ancestors’ lifestyles.)

The Theory Behind Intermittent Fasting: Returning to Natural Eating

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Like what you just read? Read the rest of the world's best book summary and analysis of Dave Asprey's "Fast This Way" at Shortform.

Here's what you'll find in our full Fast This Way summary:

  • Why intermittent fasting is more than just a way to lose weight
  • How our modern eating habits differ from our bodies' natural eating patterns
  • An intermittent fasting method that makes it easier and more enjoyable

Becca King

Becca’s love for reading began with mysteries and historical fiction, and it grew into a love for nonfiction history and more. Becca studied journalism as a graduate student at Ohio University while getting their feet wet writing at local newspapers, and now enjoys blogging about all things nonfiction, from science to history to practical advice for daily living.

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