Is Intermittent fasting better than limiting your calories for weight loss?

Bottom Line:

In this randomized controlled study of 100 obese adults, alternate day fasting was not better than simply cutting your daily calories when it came to weight loss. Also, there was no difference in terms of blood pressure, cholesterol or blood sugar between the 2 groups.

Why this matters:

Intermittent fasting has been gaining a lot of attention lately and there aren’t any good studies looking at outcomes over 6 months. The question is whether it is superior to traditional calorie restriction?

Study Design:

This was a single-center, randomized study of 100 obese adults (age 18-64 with average BMI of 34). The study was 12 months with a 6-month weight loss phase followed by a 6-month weight maintenance phase.  The participants were randomized to 3 groups:

  1. Alternate day fasting: consumed 25% of energy on fasting days and 125% of energy on alternating non-fasting days.
  2. Calorie restriction group: consumed 75% of energy daily.
  3. Control group: no intervention.

Key Findings:

  • Dropout rate was highest in alternate-day fasting group at 38%; daily caloric restriction dropout was 29%; Control group dropout was 26%.
  • No difference in overall calorie restriction between alternate-day fasting group and calorie restriction group at 6 months.
  • At the end of study (12 months), alternate day fasting group had -6% (95% CI, -8.5% to -3.6%) weight loss and -5.3% (95% CI, -7.6% to -3.0%) for the calorie restriction group. The difference between the groups was not statistically significant.
  • There were no significant differences in blood pressure, cholesterol or glucose between alternate-day fasting and calorie restriction.


  • The study included healthy obese people. Would the results have been different in diabetics?
  • The weight loss phase was only 6 months. A longer weight loss phase would help to tease out differences.


Trepanowski JF, Kroeger CM, Barnosky A, Klempel MC, Bhutani S, Hoddy KK,… Varady KA. Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults. A Randomized Clinical Trial. JAMA Intern Med. Published online May 01, 2017. doi:10.1001/jamainternmed.2017.0936.

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Sean Hashmi MD
Articles: 56

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