Does fasting help or hurt metabolism?
Written by
Robert Kelly
Reviewed by
Prof. Graham Pierce, Ph.D.The metabolic effect of fasting is entirely variable, depending on the length and method. Prolonged fasting triggers survival responses that significantly reduce metabolic rate. Brief intermittent fasting can offer slight benefits, but it is not ideal. I promote sustainable nutrition methods as an alternative to fasting.
Prolonged Fasting
- Triggers metabolic adaptation reducing calorie burn by 15-30%
- Causes muscle loss decreasing resting metabolic rate
- Leads to rebound weight gain after resuming eating
Intermittent Fasting
- May increase norepinephrine temporarily boosting alertness
- Limited metabolic benefits beyond calorie restriction
- Works best for those with insulin resistance issues
Extended fasting triggers energy-preserving adaptations. The body reduces its production of thyroid hormones and slows the metabolic processes within the cells. This adaptation persists even after eating is resumed, resulting in a metabolic slowdown. I have seen this effect in clients with metabolic testing.
For most, intermittent fasting gives minimal metabolic benefit. The short-term increase in norepinephrine does not result in a significant increase in calorie burning. Weight comes off by restricting calories rather than increasing metabolism. Results are individualized considerably, depending on the individual's biological makeup.
Preserving protein prevents the decline of metabolism more than fasting. Muscle mass will be maintained and metabolism will remain elevated when consuming 1.6-2.2 grams per kilogram. Protein should be consumed around the time of training to achieve a beneficial effect on muscle protein synthesis. This method yields the most effective long-term results for maintaining metabolic health.
Strength training creates muscle that consistently burns calories. Each pound of muscle increases resting metabolism by 6-10 calories per day. This provides a pace-setting boost to the resting metabolic rate that lasts longer than fasting. Two sessions a week generate cumulative benefits through time.
Concentrate on maintaining continuous nutrition patterns rather than avoiding them. We aim for balanced meals with sufficient protein to support metabolic function. Additionally, combining this program with a resistance training regimen yields the most beneficial results. This all avoids the metabolic damage done by extreme fasting protocols.
Read the full article: 10 Effective Ways to Boost Metabolism
