Intermittent fasting
Intermittent fasting is an eating pattern that alternates defined periods of eating with periods of little or no energy intake. It controls when food is eaten rather than prescribing a particular food list. Common forms include daily time-restricted eating, alternate-day fasting, and the 5:2 pattern with two very-low-intake days per week.
Rules differ between protocols. Water and noncaloric drinks are often allowed during a fast, but milk, sugar, juice, alcohol, and other calorie-containing drinks end a zero-calorie fast. A religious fast may use different rules, and a daily overnight fast of ordinary length is not usually what fitness discussions mean by intermittent fasting.
Intermittent fasting can support fat loss when it makes a calorie deficit easier to maintain; the fasting window does not override energy balance. A 2026 Cochrane review found little to no meaningful difference in weight loss or quality of life compared with standard dietary advice for adults with overweight or obesity, with limited reporting of adverse events. It is best viewed as one scheduling option rather than a superior metabolic method.
Strength training can be combined with fasting, but a narrow eating window may make it harder to consume enough total energy and distribute protein across several meals. Training quality can also suffer if a demanding session falls late in a long fast. Placing the session near an eating period, keeping protein and hydration adequate, and watching actual performance are more useful than assuming fasted training burns more body fat over time.
Intermittent fasting is not appropriate for everyone. Australian government health guidance advises against it for children and adolescents, people who are pregnant or breastfeeding, and anyone with a current or past eating disorder; some medical conditions also require advice first. Diabetes medication can make fasting-related low blood glucose dangerous, so medication should never be adjusted without the treating clinician.