Fasting & meal-timing approaches
Alternate-day fasting
Alternates normal eating days with fasting or very-low-calorie days, a more intensive fasting schedule than 5:2.
What people typically eat
Normal meals on eating days; either nothing or around 500 kcal on fasting days.
What is restricted
Roughly half of all days carry severe restriction.
Why people try it
Faster weight loss than weekly fasting patterns, and interest in metabolic research.
Realistic advantages
- Produces meaningful weight loss in trials
- No food rules on eating days
- One of the better-studied fasting protocols
Realistic disadvantages
- One of the hardest patterns to sustain, dropout rates are high
- Hunger does not fully adapt even after weeks for many people
- Trials show no clear advantage over ordinary daily calorie restriction
Strength of evidence
Limited evidence
Adequate short-term trials, but high dropout and no demonstrated long-term superiority.
Key studies
- Trepanowski et al., JAMA Internal Medicine, 2017. Alternate-day fasting produced similar weight loss to daily calorie restriction, with higher dropout rates.
Likely cost and difficulty
Low cost; very high difficulty.
Nutritional risks
Fatigue, irritability, and over-restriction in people prone to disordered eating.
Who should avoid it
Pregnancy, adolescence, eating-disorder history, diabetes on medication, and physically demanding jobs on fast days.
Is professional supervision advisable?
Advisable, this is an intensive protocol.
References
Written by the Slimr editorial team. How we review diets.
