EvidenceBModerateGood evidence in people with one real weakness. New studies could change the answer.
Mostly no. Intermittent fasting and cutting calories every day lead to about the same weight loss. Alternate-day fasting may edge ahead by roughly 1 kg in shorter trials.
Who it's for
Adults with overweight who find fasting easier to stick with than daily dieting.
What to expect
Similar weight loss either way; alternate-day fasting may add about 1 kg.
Watch out for
Alternate-day fasting had more dropouts, and one trial saw higher LDL cholesterol.
Fasting and calorie cutting give similar weight loss
Each dot is the weight difference of a fasting approach versus calorie cutting, with a line showing the likely range; lines crossing zero mean no clear difference.
← BetterWorse →
No difference
Alternate day fasting (meta-analysis)−1.29 (−1.99 to −0.59)Clear improvement
Time-restricted eating (12-month trial)−1.8 (−4 to 0.4)No clear difference
Time-restricted eating (12-week trial)−0.26 (−1.3 to 0.78)No clear difference
All fasting types combined (meta-analysis)−0.42 (−0.96 to 0.13)No clear difference
−4−20
kg difference vs calorie cutting, 0 = same
Fasting and calorie cutting give similar weight loss
The National Institute on Aging says there isn't enough evidence to recommend any fasting or calorie-restriction regimen to the public1Guideline · 2018Calorie Restriction and Fasting Diets: What Do We Know?In CALERIE, 218 young and middle-aged, normal-weight or moderately overweight adults were randomly divided into two groups. Overall, these findings indicate that while the degree of calorie restriction in CALERIE is safe for normal-weight or moderately obese people, clinical monitoring is recommended.National Institute on Aging (NIH).
What the studies show
A review that pooled 99 trials in 6,582 adults found all fasting plans and daily calorie cutting beat eating freely. Alternate-day fasting beat daily calorie cutting by about 1.3 kg, with moderate certainty2Meta-analysis · 2025 · 6,582 peopleIntermittent fasting strategies and their effects on body weight and other cardiometabolic risk factors: systematic review and network meta-analysis of randomised clinical trials.Minor differences were noted between some intermittent fasting diets and continuous energy restriction, with some benefit of weight loss with alternate day fasting in shorter duration trials. The current evidence provides some indication that intermittent fasting diets have similar benefits to continuous energy…BMJ.
In that review, the edge appeared in trials under 24 weeks. In 17 longer trials (24 weeks or more), fasting showed no advantage over daily calorie cutting2Meta-analysis · 2025 · 6,582 peopleIntermittent fasting strategies and their effects on body weight and other cardiometabolic risk factors: systematic review and network meta-analysis of randomised clinical trials.Minor differences were noted between some intermittent fasting diets and continuous energy restriction, with some benefit of weight loss with alternate day fasting in shorter duration trials. The current evidence provides some indication that intermittent fasting diets have similar benefits to continuous energy…BMJ.
A review of 28 trials in healthy adults, lasting 2 to 52 weeks, found no clear difference in weight or fat loss. Fasting plans combined lost slightly more muscle and waist size5Meta-analysis · 2024Effects of Intermittent Energy Restriction Compared with Those of Continuous Energy Restriction on Body Composition and Cardiometabolic Risk Markers - A Systematic Review and Meta-Analysis of Randomized Controlled Trials in Adults.Slightly greater reductions were, however, observed in fat-free mass and waist circumference. To what extent differences in energy intakes between groups within studies may have influenced these outcomes should be addressed in future studies.Adv Nutr.
A review of 27 trials found 12 that compared fasting with calorie cutting, and all found equivalent results8Systematic review · 2020 · 244 peopleIntermittent fasting and weight loss: Systematic review.Intermittent fasting shows promise for the treatment of obesity. To date, the studies have been small and of short duration. Longer-term research is needed to understand the sustainable role IF can play in weight loss.Can Fam Physician. Another pooled analysis found a small edge for fasting on weight but none on BMI9Meta-analysis · 2022Intermittent Fasting versus Continuous Calorie Restriction: Which Is Better for Weight Loss?848) between IF and CCR. These findings suggest that IF may be superior to CCR for weight loss in some respects.Nutrients.
A trial of 100 obese adults over 1 year found alternate-day fasting gave no better weight loss than daily cutting. Dropout was higher with fasting (38% vs 29%), and LDL cholesterol rose more7Randomized trial · 2017 · 100 peopleEffect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults: A Randomized Clinical Trial.Alternate-day fasting did not produce superior adherence, weight loss, weight maintenance, or cardioprotection vs daily calorie restriction.JAMA Intern Med.
Time-restricted eating (eating only within a set window) did not beat calorie cutting in a 12-month trial of 139 people with obesity3Randomized trial · 2022 · 139 peopleCalorie Restriction with or without Time-Restricted Eating in Weight Loss.Among patients with obesity, a regimen of time-restricted eating was not more beneficial with regard to reduction in body weight, body fat, or metabolic risk factors than daily calorie restriction. (Funded by the National Key Research and Development Project [No. 2018YFA0800404] and others; ClinicalTrials.gov number,…N Engl J Med or in a 12-week trial of 116 people6Randomized trial · 2020 · 116 peopleEffects of Time-Restricted Eating on Weight Loss and Other Metabolic Parameters in Women and Men With Overweight and Obesity: The TREAT Randomized Clinical Trial.Time-restricted eating, in the absence of other interventions, is not more effective in weight loss than eating throughout the day.JAMA Intern Med. In a 6-month trial of 75 adults with type 2 diabetes, it did better on weight than counting calories, but that trial was small10Randomized trial · 2023 · 53 peopleEffect of Time-Restricted Eating on Weight Loss in Adults With Type 2 Diabetes: A Randomized Clinical Trial.This randomized clinical trial found that a TRE diet strategy without calorie counting was effective for weight loss and lowering of HbA1c levels compared with daily calorie counting in a sample of adults with T2D. These findings will need to be confirmed by larger RCTs with longer follow-up.JAMA Netw Open.
Review results compare groups, so the gain for one person depends on where they start.
Key studies
Study
Who
What it found
Review of 99 trials, 20252Meta-analysis · 2025 · 6,582 peopleIntermittent fasting strategies and their effects on body weight and other cardiometabolic risk factors: systematic review and network meta-analysis of randomised clinical trials.Minor differences were noted between some intermittent fasting diets and continuous energy restriction, with some benefit of weight loss with alternate day fasting in shorter duration trials. The current evidence provides some indication that intermittent fasting diets have similar benefits to continuous energy…BMJ
6,582 adults
Alternate-day fasting about 1.3 kg better; gone in long trials
Review of 28 trials, 20245Meta-analysis · 2024Effects of Intermittent Energy Restriction Compared with Those of Continuous Energy Restriction on Body Composition and Cardiometabolic Risk Markers - A Systematic Review and Meta-Analysis of Randomized Controlled Trials in Adults.Slightly greater reductions were, however, observed in fat-free mass and waist circumference. To what extent differences in energy intakes between groups within studies may have influenced these outcomes should be addressed in future studies.Adv Nutr
Healthy adults
No clear weight difference from calorie cutting
Trial, 20177Randomized trial · 2017 · 100 peopleEffect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults: A Randomized Clinical Trial.Alternate-day fasting did not produce superior adherence, weight loss, weight maintenance, or cardioprotection vs daily calorie restriction.JAMA Intern Med
100 obese adults
Same weight loss at 1 year; more dropouts with fasting
Trial, 20223Randomized trial · 2022 · 139 peopleCalorie Restriction with or without Time-Restricted Eating in Weight Loss.Among patients with obesity, a regimen of time-restricted eating was not more beneficial with regard to reduction in body weight, body fat, or metabolic risk factors than daily calorie restriction. (Funded by the National Key Research and Development Project [No. 2018YFA0800404] and others; ClinicalTrials.gov number,…N Engl J Med
139 people with obesity
Time-restricted eating no better at 12 months
Trial, 202310Randomized trial · 2023 · 53 peopleEffect of Time-Restricted Eating on Weight Loss in Adults With Type 2 Diabetes: A Randomized Clinical Trial.This randomized clinical trial found that a TRE diet strategy without calorie counting was effective for weight loss and lowering of HbA1c levels compared with daily calorie counting in a sample of adults with T2D. These findings will need to be confirmed by larger RCTs with longer follow-up.JAMA Netw Open
75 adults with type 2 diabetes
Time-restricted eating lost more weight than calorie counting
Safety
Trials reported no serious side effects from fasting8Systematic review · 2020 · 244 peopleIntermittent fasting and weight loss: Systematic review.Intermittent fasting shows promise for the treatment of obesity. To date, the studies have been small and of short duration. Longer-term research is needed to understand the sustainable role IF can play in weight loss.Can Fam Physician,10Randomized trial · 2023 · 53 peopleEffect of Time-Restricted Eating on Weight Loss in Adults With Type 2 Diabetes: A Randomized Clinical Trial.This randomized clinical trial found that a TRE diet strategy without calorie counting was effective for weight loss and lowering of HbA1c levels compared with daily calorie counting in a sample of adults with T2D. These findings will need to be confirmed by larger RCTs with longer follow-up.JAMA Netw Open. Alternate-day fasting had higher dropout and higher LDL cholesterol in one trial7Randomized trial · 2017 · 100 peopleEffect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults: A Randomized Clinical Trial.Alternate-day fasting did not produce superior adherence, weight loss, weight maintenance, or cardioprotection vs daily calorie restriction.JAMA Intern Med. Calorie restriction in healthy, normal-weight or moderately overweight adults was safe with clinical monitoring1Guideline · 2018Calorie Restriction and Fasting Diets: What Do We Know?In CALERIE, 218 young and middle-aged, normal-weight or moderately overweight adults were randomly divided into two groups. Overall, these findings indicate that while the degree of calorie restriction in CALERIE is safe for normal-weight or moderately obese people, clinical monitoring is recommended.National Institute on Aging (NIH).
What we don't know
Whether alternate-day fasting's small edge lasts beyond 6 months; longer trials show none2Meta-analysis · 2025 · 6,582 peopleIntermittent fasting strategies and their effects on body weight and other cardiometabolic risk factors: systematic review and network meta-analysis of randomised clinical trials.Minor differences were noted between some intermittent fasting diets and continuous energy restriction, with some benefit of weight loss with alternate day fasting in shorter duration trials. The current evidence provides some indication that intermittent fasting diets have similar benefits to continuous energy…BMJ.
Whether results hold for older adults or people with other health conditions, as few trials studied them.
Written by AI from the studies listed, without review by a clinician, and graded with the GRADE method. It can be wrong, so check the studies it cites. Education, not medical advice.