"This new study by Templeman et al. doesn't look good for people that like long intermittent fasts.
The researchers compared weight loss diets with 25% constant daily energy restriction vs. complete alternate day fasting with 0% energy intake during the 24-hour fasts and 150% energy intake in between. The study was in healthy adults.
So same weekly energy intake and macros but either with long fasting or without.
The fasting group lost less body fat, probably because they experienced a significant reduction in energy expenditure from physical activity, especially later on into the fasts.
Several other studies have pointed to reductions in physical activity level during fasting, which is why I don't recommend intermittent fasting (IF) during periods of high physical activity, and not fasting too long in general.
The fasting group also lost considerably more lean body mass, although this was not significantly different from the other group.
Moreover, the fasting did not result in significant cardiometabolic health improvements, including insulin sensitivity and blood blood sugar levels after eating.
And the kicker: the fasting did not result in favorable changes in gene expression of inflammation and autophagy.
My recommendations:
- Don't fast during prolonged periods of high physical activity.
- Don't fast more than ~20 hours, preferably no more than ~16.
- If you want to implement short, aggressive deficits in your diet, do protein sparing modified fast (PSMF) periods: maintain a high protein intake during the 'fast' to keep your metabolism up and prevent muscle loss."- Menno Henselmans
