“Intermittent fasting works for weight loss.”
Intermittent fasting does help people lose weight, usually a modest amount, about the same as cutting calories in other ways.
A fasting schedule is a real, workable way to lose some weight, mostly because it helps you eat less. Expect a modest loss, about what any other calorie-cutting plan gives, not a dramatic one. If an eating window fits your day and you can keep it up, it is a reasonable choice. Whether fasting beats a regular diet is covered in our card "Intermittent fasting is better for weight loss than a regular calorie-controlled diet."
If fasting appeals to you, try one simple eating window, such as noon to 8 PM, for four weeks and see whether you can keep it up.
Safety note: Fasting can cause low blood sugar in people who take insulin or sulfonylurea pills (such as glipizide or glimepiride) for diabetes, so these doses usually need to be adjusted on fasting days.
Talk to a healthcare professional if: you take insulin or a sulfonylurea for diabetes and want to try fasting.
A 99-trial analysis found that every fasting style took off weight compared with eating freely, and a Cochrane review and a 12-month trial found the same against no diet at all. The loss is modest and no better than regular calorie cutting, most trials lasted a year or less, and the Cochrane authors judged the gain over no diet too small to be clearly meaningful, so the verdict is Mostly true with Moderate confidence.
Intermittent fasting does help people lose weight, usually a modest amount, about the same as cutting calories in other ways. In a Cochrane review, people who fasted lost about 3.4 percent more of their body weight than people given no diet, across 6 trials followed for 6 months or more. In a 12-month trial of 90 adults with obesity, eating only between noon and 8 PM, without counting calories, took off about 10 pounds more than the control group.
In a 2025 analysis of 99 trials with 6,582 adults, every style of intermittent fasting (eating within a daily time window, alternate-day fasting, and whole-day fasting once or twice a week) reduced weight compared with eating freely, including in the 17 trials lasting about 6 months or longer. Fasting seems to work by helping people eat less: in the 12-month trial, the time-window group ate about 425 fewer calories a day, close to the 405 fewer in the calorie-counting group, and both lost similar weight. As an illustration only, 3.4 percent of body weight would be about 7 pounds for a 200-pound person.
- Garegnani LI, Oltra G, Ivaldi D, Burgos MA, Andrenacci PJ, Rico S, Boyd M, Radler D, Escobar Liquitay CM, Madrid E. Intermittent fasting for adults with overweight or obesity. Cochrane Database of Systematic Reviews. 2026;2:CD015610. DOI: 10.1002/14651858.CD015610.pub2. PMID: 41692034
- Semnani-Azad Z, Khan TA, Chiavaroli L, et al. Intermittent fasting strategies and their effects on body weight and other cardiometabolic risk factors: systematic review and network meta-analysis of randomised clinical trials. BMJ. 2025;389:e082007. DOI: 10.1136/bmj-2024-082007. PMID: 40533200. PMCID: PMC12175170
- Lin S, Cienfuegos S, Ezpeleta M, Gabel K, Pavlou V, Mulas A, Chakos K, McStay M, Wu J, Tussing-Humphreys L, Alexandria SJ, Sanchez J, Unterman T, Varady KA. Time-Restricted Eating Without Calorie Counting for Weight Loss in a Racially Diverse Population: A Randomized Controlled Trial. Annals of Internal Medicine. 2023;176(7):885-895. DOI: 10.7326/M23-0052. PMID: 37364268. PMCID: PMC11192144
- Grajower MM, Horne BD. Clinical Management of Intermittent Fasting in Patients with Diabetes Mellitus. Nutrients. 2019;11(4):873. DOI: 10.3390/nu11040873. PMID: 31003482. PMCID: PMC6521152