February 4, 2024October 31, 2026

The Pros and Cons of Fasting: What You Need to Know

Possible health gains set against real risks

Fasting means going without food, and sometimes drink, for a set period. People have done it for centuries, in many cultures and religions. Today some fast for religious or spiritual reasons, while others hope it will improve their health.

Maybe you are thinking of intermittent fasting, time-restricted eating, or another method. Either way, it helps to know what fasting may do for you and where it can go wrong, so here are some of the main points on both sides.

Pros

Much of the evidence for these benefits is still early. Read them as possibilities.

Improved metabolic health
Fasting can help regulate blood sugar and make the body more sensitive to insulin, which generally means better metabolic function. It may also help with weight management and lower the risk of developing type 2 diabetes, although results vary from person to person.
Better brain function
Fasting may protect nerve cells and could improve brain function, though the evidence so far is limited. It has been linked to increased neuronal autophagy, the process in which cells break down and clear out their own worn parts. That might support cognitive resilience and the health of the brain in general.
Possible longevity benefits
Fasting might also help people live longer. The idea is that it influences processes inside cells and promotes cellular repair, which could contribute to a longer, healthier life. Of the benefits listed here, this one is probably the least settled.
Less inflammation
Fasting appears to lower inflammation in the body. Because chronic inflammation is tied to heart disease, diabetes, and cancer, that may reduce the risk of those diseases. The usual explanation is that when the digestive system gets a break, the body can put more effort into repairing cells and tissues, and inflammation drops as a result.
Stronger immune function
Intermittent fasting has been linked to better immune function, possibly because it helps regulate how the body produces immune cells. If that holds, the result could be a stronger immune response and better protection against infections and disease.

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Cons

How much these drawbacks matter depends a lot on who you are and how long or how often you fast.

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Possible nutrient deficiencies
Long fasts can leave you short of nutrients. Many essential vitamins and minerals come mainly from food, and over extended periods without it you may not get enough of them. That can affect your health over time.
Risk of disordered eating
Some people are prone to disordered eating, and fasting can push them further in that direction. The risk is greatest when it leads to unhealthy eating habits or to an obsessive focus on food and restriction.
Not suitable for everyone
Fasting does not suit everyone. People with certain medical conditions, women who are pregnant or breastfeeding, and anyone with a history of eating disorders need to be especially careful. Your own health situation should weigh more heavily than general advice.
Possible effects on hormones
In some people, long or frequent fasting can throw hormones off balance. Women may get irregular menstrual cycles, and stress hormones such as cortisol can shift as well. Anyone who fasts should watch for signs like these.
Social and psychological strain
A lot of social life revolves around food, so fasting can be awkward at gatherings and events built around a meal. There is a mental side too. For some people fasting brings stress and anxiety, and if they keep going without paying attention to how they feel, their mental well-being can suffer.

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Conclusion

If you have a medical condition, are pregnant or breastfeeding, or have had an eating disorder, talk to a doctor before you start. That advice holds for everyone else too. Since several of the risks are tied to long or frequent fasts, a shorter approach such as time-restricted eating is probably the easier place to begin.