Intermittent fasting (IF) has become a popular, largely self-prescribed dietary strategy, with approximately 10 to 15 percent of U.S. adults practicing some form of it, and up to one in three report having tried it. Its most common purpose is for weight loss or metabolic health. Its appeal is simple: focus on when to eat rather than what to eat.

The most common version is time restricted eating, typically structured as a 16 hour fasting period followed by an 8 hour eating window, such as noon to 8 p.m. Other approaches include alternate day fasting or fasting one to two days per week. Most individuals adopt a form of IF independently after exposure through media, books, or social platforms, though some physicians or registered dietitians may recommend it selectively based on unique patient needs, schedules, preferences, and/or chances of long term sustainability for the individual.

Evidence and Comparison With Other Dietary Approaches

Research shows that intermittent fasting can lead to modest weight loss, but it is not superior to traditional approaches such as basic calorie restriction. A 12 month randomized controlled trial published in JAMA Internal Medicine compared a 16:8 time restricted eating schedule with daily calorie restriction in adults with overweight or obesity. Both groups lost similar amounts of weight, approximately 4 to 6 pounds over one year, with no significant metabolic advantage in the fasting group. A review in The New England Journal of Medicine concluded that improvements in weight, blood pressure, and insulin sensitivity observed with intermittent fasting are largely explained by reduced overall calorie intake rather than a unique metabolic mechanism. Likewise, a meta-analysis in Obesity Reviews found comparable weight loss between intermittent energy restriction and continuous calorie restriction when calories were matched.

The primary reason intermittent fasting works appears behavioral. Limiting eating time reduces opportunities to consume calories. Although fasting temporarily lowers insulin levels and increases fat oxidation, total energy balance remains the dominant factor in weight regulation.

Other weight loss strategies more directly target behavior and food quality. Data from the National Weight Control Registry, which tracks more than 10,000 individuals who have maintained at least a 30 pound weight loss for one year or longer, show that consistent portion monitoring, calorie awareness, and regular self-weighing are common among long term weight-loss maintainers.

Food choice also strongly influences intake. In a controlled inpatient study conducted by the National Institutes of Health, participants consuming an ultra-processed diet ate about 500 more calories per day than when consuming a minimally processed whole food diet, despite similar

macronutrient composition. The ultra processed diet led to weight gain, while the minimally processed diet led to weight loss. These findings suggest that emphasizing whole foods may better support natural satiety signaling than simply restricting eating windows.

Sustainability and Conclusion

Because intermittent fasting does not inherently change food quality or eating habits, individuals who return to extended eating periods without modifying intake may regain weight. Reviews note adherence challenges comparable to other dietary approaches.

Intermittent fasting may suit individuals who prefer structured time limits. However, sustainable weight management consistently aligns with achieving an appropriate calorie balance, emphasizing minimally processed foods, and maintaining regular physical activity. A registered dietitian specializing in weight management can help determine the most appropriate strategy, monitor health markers, and build habits that support long term success.

About the Author

Patrick Traynor, PhD, MPH, RD, CSOWM, CPT, is a registered dietitian and founder of MNT Scientific, LLC (MNTScientific.com), an insurance-based nutrition practice serving South Lake Tahoe, CA; Minden, NV; and Ashland, OR. He holds the Interdisciplinary Specialist Certification in Obesity and Weight Management (CSOWM) from the Commission on Dietetic Registration. Virtual appointments are available via telehealth. For inquiries or appointments, visit MNTScientific.com, dial (530)429-7363, or email info@mntscientific.com.