Intermittent fasting has become very popular in recent years, especially among people trying to lose weight or improve their health. It involves having set hours for eating and longer periods when you don’t eat at all.
Many diets focus on what to eat, but intermittent fasting is all about when you eat.
There are several common types of intermittent fasting, including:
Alternate-day fasting – eating one day and fasting the next
Modified alternate-day fasting – eating very small amounts on fasting days
5:2 fasting – eating normally for five days and very little on two days
Time-restricted eating – eating only within a set time window each day2
Intermittent Fasting: Benefits and Risks
Research shows that intermittent fasting doesn’t just help with weight it triggers a “metabolic switch” that can benefit the body and brain. Supporters of intermittent fasting believe that giving the body a break from constant eating helps improve insulin levels, support hormone balance, and allow the body to repair itself. It:
Supports brain health – May improve memory and thinking skills
Protects the heart – Can lower blood pressure and resting heart rate
Helps with weight loss – Promotes fat loss while preserving muscle
Improves diabetes control – May lower fasting sugar, insulin levels, and insulin resistance
Reduces inflammation – Helps protect organs from long-term damage
Supports cell repair – Animal studies show better healing and tissue protection1,3
However, it is important to note that intermittent fasting is not for everyone. Some people may experience:
Headache, fatigue, or irritability
Constipation or dizziness
Strong hunger leading to overeating
Blood sugar swings, especially in people with diabetes
Too much weight loss in older adults or underweight people2,3
How Intermittent Fasting Affects Hormonal Health
Research suggests that intermittent fasting may help reset the body’s natural daily rhythm (also called the circadian clock). This rhythm plays a major role in keeping hormones balanced. Fasting periods can improve how insulin works, which helps control blood sugar, and may also influence thyroid hormones, stress hormones like cortisol, and sex hormones.4
As far as reproductive hormones are concerned research shows that:
In women with obesity, intermittent fasting may lower testosterone-like hormones while increasing a hormone-binding protein (SHBG). This can be helpful for women with PCOS, where high testosterone causes irregular periods, acne, and fertility problems. These effects are stronger when meals are eaten earlier in the day.
In men, intermittent fasting has been found to slightly lower testosterone in young, active individuals. However, muscle strength and physical performance were not affected. Still, lower testosterone over time could impact energy, mood, and libido.5
Intermittent fasting may also improve gut health. A healthier gut supports better hormone balance and reduces inflammation, which is linked to conditions like diabetes, heart disease, and even some cancers.4
Is Intermittent Fasting Safe?
Intermittent fasting is popular for weight loss and health, but it isn’t right for everyone. While some people use it to manage conditions like high cholesterol, arthritis, or digestive problems, fasting can be risky for certain groups.1
You should avoid intermittent fasting if you are:
Under 18 years of age
Pregnant or breastfeeding
Living with diabetes or using insulin or have frequent low blood sugar
Recovering from or having a history of eating disorders
Take medicines for blood pressure, heart disease, or that must be taken with food
Are elderly, underweight, or have a long-term illness2,3
If you feel dizzy, anxious, nauseous, or unwell after starting intermittent fasting, stop and speak with your doctor.