7 intermittent fasting myths you should stop believing
It eats your muscle, it slows your metabolism, you have to eat breakfast… we take apart the most repeated myths about fasting.
Part of the complete guide Intermittent fasting for weight loss: what actually works
What the science says7 intermittent fasting myths, debunked
The most repeated intermittent fasting myths do not hold up: short fasts do not slow your metabolism (in an 84-hour fast, resting expenditure actually rises), they do not destroy muscle when protein and strength training are in place, skipping breakfast does not make you gain weight, and black coffee does not break your fast. Fasting alone will not slim you down either: no calorie deficit, no weight loss.
- Resting energy expenditure rose from 3.97 to 4.53 kJ/min by day 3 of an 84 h fast in 11 lean adults (Zauner 2000). [1]
- Meta-analysis of 13 trials: breakfast eaters took in about 260 kcal/day more and weighed 0.44 kg more than skippers (Sievert 2019). [2]
- 16/8 plus strength training for 8 weeks: less fat, with fat-free mass and maximal strength preserved (Moro 2016). [3]
Myth 1: it slows your metabolism
False for short fasts. Fasts of 16-24 h do not slow your metabolism; some studies even show a slight short-term bump. What does lower it is a very aggressive, prolonged calorie deficit, fasting or not.
Myth 2: it eats your muscle
With enough protein and some strength training, short fasting does not destroy muscle. Your body goes for fat first. Muscle loss comes from aggressive deficits with too little protein.
Myth 3: you have to eat breakfast
Breakfast being the most important meal of the day is cereal marketing, not science. Skipping breakfast does not make you gain weight or harm you as long as your overall diet is solid.
Myth 4: coffee breaks your fast
Black coffee does not break your fast (under 5 kcal). Milk and sugar do. Drink it without worry during your fast.
Myth 5: you will be starving forever
Hunger is mostly a first-week thing. After that the body adapts, and many people stop being hungry in the morning.
Myth 6: the longer you fast, the better
Nope. More hours is not always better. Extreme daily fasts can bring hormonal and muscle problems. Sustainable consistency beats intensity.
Myth 7: fasting alone makes you lose weight
Fasting makes a deficit easier, but if you binge in your window, you will not lose weight. It organizes when you eat; it does not excuse you from watching how much.
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Frequently asked questions
Does intermittent fasting slow your metabolism?
Is it true that you always have to eat breakfast?
Scientific sources (4)
- Resting energy expenditure in short-term starvation is increased as a result of an increase in serum norepinephrine. The American Journal of Clinical Nutrition, 2000.
- Effect of breakfast on weight and energy intake: systematic review and meta-analysis of randomised controlled trials. BMJ, 2019.
- Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males. Journal of Translational Medicine, 2016.
- Effects of Intermittent Fasting on Health, Aging, and Disease. New England Journal of Medicine, 2019.