Does Intermittent Fasting Work?

A silver knife and fork are arranged in parallel atop a white plate. Between the utensils, there is an old fashioned analogue alarm clock. The plate has no food on it symbolizing intermittent fasting.
  • April 23, 2024

Most diets focus on what to eat, but intermittent fasting focuses on when to eat. This means fasting for a set time each day or each week. The majority of people who try intermittent fasting do so for weight loss, while others use it to address chronic health conditions. Before committing to a fasting schedule, let's learn more about the practice and how it might affect your body.


How does it work?

Intermittent fasting works by extending the length of time between when your body has burned through the calories consumed during your last meal and when it begins burning fat.

To date, most research on this topic has been done on rats. These rats do see benefits. They lose weight and improvements are seen in age-related disorders, including diabetes, cardiovascular disease, and neurological disorders. But, what about research on humans? Human studies, while limited in number, have shown similar results. However, the results are no better than eating less every day. Another caveat is that the potential health benefits are not known to be caused by intermittent fasting, or the subsequent weight loss (or both).

There are many approaches.

The most popular variations to include fasting into your diet include:

  • Alternate-Day Fasting – Eat normally one day, then fast completely or have only one small meal the next day.
  • 5:2 Fasting – Eat normally 5 days per week and fast completely (or only eat one small meal) for 2 nonconsecutive days per week.
  • Time-Restricted Fasting – Eat normally within an 8- or 12-hour window each day and fast the remaining 16 or 12 hours.

For most intermittent fasting diets, it’s recommended that you only drink zero-calorie beverages during the fasting period. During the eating period, “eating normally” certainly does not mean eating anything you want. It means eating sensibly. If you “go crazy” and gorge yourself on fried and processed foods, you’re likely to not lose weight or become healthier. In fact, the opposite could happen.

Is it safe for everyone?

Intermittent fasting is not recommended for the following groups of people:

  • Children
  • Women who are pregnant or breastfeeding
  • Individuals with higher nutrient needs
  • Type 1 diabetics or those with blood sugar problems
  • Cancer patients at risk for malnutrition
  • Nutritionally-compromised patients
  • Those with a history of eating disorders

As with any diet, there are always potential drawbacks. With intermittent fasting, these can include:

  • Disordered eating behaviors
  • Disrupted sleep
  • Decreased alertness
  • Increased guilt
  • Increased cortisol levels (stress hormone)
  • Higher LDL levels
  • Pancreatic damage

So, what does all of this mean?

Compared to other diets, intermittent fasting does not seem to provide an advantage for weight loss or overall health. This type of diet focuses on WHEN to eat, but WHAT to eat is even more important for optimal health. Instead of intermittent fasting, I recommend a nutritious plant-based eating plan that focuses on mindful eating. An eating plan that emphasizes fruits, vegetables, beans, lentils, whole grains, lean proteins, fat-free dairy, and healthy fats – in other words, an eating plan like Pritikin! – will do wonders for your health. Eating mindfully involves being more aware of the food’s preparation, taste, satisfaction, and satiety factor. Last, but not least, remember that intermittent fasting can have different effects on different people. If you still decide to try intermittent fasting, be sure to first consult with your doctor or registered dietitian.

This article was originally published on 8/13/2020.

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