Scientists reviewed research on intermittent fasting—eating during certain times and fasting during others—to understand how it affects your body’s hormones and health. The review found that intermittent fasting may help reset your body’s natural rhythms, improve how your body handles sugar, and potentially reduce inflammation. However, researchers warn that most studies so far have been small or short-term, so we need bigger, longer studies to know if it’s truly safe and effective for everyone, especially over many years.

The Quick Take

  • What they studied: How intermittent fasting (eating during set times, fasting during others) affects your body’s hormones, metabolism, and disease risk
  • Who participated: This was a review of many existing studies involving both humans and animals; no single group of participants
  • Key finding: Intermittent fasting appears to change how your body produces and uses hormones like insulin and thyroid hormones, potentially helping your body work more efficiently and reducing inflammation
  • What it means for you: Intermittent fasting may be a helpful tool for some people, but it’s not a proven cure-all. More research is needed before doctors can confidently recommend it for specific health conditions. Talk to your doctor before starting any fasting plan, especially if you have health conditions or take medications

The Research Details

This was a review article, meaning scientists looked at and summarized findings from many different studies about intermittent fasting. They examined research from both human studies and animal experiments to understand how fasting affects hormones. The researchers focused on studies that measured actual hormone levels and tracked how the body changed with different fasting schedules. They looked at various fasting methods, such as eating only during certain hours of the day or fasting on specific days of the week.

By reviewing many studies together, scientists can spot patterns and understand the bigger picture of how intermittent fasting works. This approach helps identify what we know for sure versus what still needs more research. It’s especially important for intermittent fasting because different studies use different methods, making it hard to compare results.

This review pulls together existing research but doesn’t present new experimental data. The quality depends on the studies reviewed. The authors note that current research has significant limitations: studies vary widely in design, most last only weeks or months (not years), and involve relatively small groups of people. These factors make it harder to know if findings apply to everyone or hold up over time.

What the Results Show

The review found that intermittent fasting appears to affect multiple hormone systems in your body. Specifically, it may improve how your body handles insulin (the hormone that controls blood sugar), adjust thyroid hormones (which control metabolism), and influence stress hormones like cortisol. These changes suggest that fasting might help your body’s natural daily rhythms work better. The research also indicates that intermittent fasting may reduce inflammation in the body, which is linked to many diseases. Additionally, the review suggests that these hormonal changes could potentially lower cancer risk, though this remains largely theoretical and needs more research to confirm.

The review found that intermittent fasting may also change your gut bacteria (microbiome), which plays a role in overall health. The timing of when you eat appears to matter—your body’s natural 24-hour rhythm influences how it responds to fasting. Sex hormones may also be affected, though the research here is less clear and may differ between men and women. These secondary effects could be important for long-term health but need more study.

This review builds on growing interest in intermittent fasting as a health strategy. Previous research suggested fasting might help with weight loss and blood sugar control. This review goes deeper, examining the hormonal mechanisms—the ‘how’ and ‘why’ behind these effects. It positions intermittent fasting as more than just a diet tool, suggesting it may work by resetting your body’s internal clock and hormone balance. However, the authors note that many questions from earlier research remain unanswered.

The review has several important limitations. First, the studies examined used different fasting schedules and methods, making direct comparisons difficult. Second, most studies lasted only weeks or months, not years, so we don’t know about long-term effects. Third, most studies involved relatively small groups of people, and results may not apply to everyone. Fourth, there’s limited research on how intermittent fasting affects different groups (men vs. women, young vs. old, people with different health conditions). Finally, while the review suggests intermittent fasting might reduce cancer risk, this is mostly theoretical—actual cancer prevention hasn’t been proven in humans yet.

The Bottom Line

Based on current evidence, intermittent fasting may be worth trying if you’re interested in improving metabolic health, but it’s not a guaranteed solution. Confidence level: Moderate for short-term metabolic effects (weeks to months), Low for long-term safety and cancer prevention. Always consult your doctor before starting intermittent fasting, especially if you have diabetes, heart disease, take medications, are pregnant, breastfeeding, or have a history of eating disorders.

People interested in metabolic health, weight management, or reducing inflammation may want to learn more. However, intermittent fasting is NOT recommended for children, pregnant women, people with eating disorders, those with uncontrolled diabetes, or anyone taking medications that require food intake. If you have any chronic health condition, talk to your doctor first.

If intermittent fasting works for you, you might notice changes in energy levels within 1-2 weeks as your body adjusts. Metabolic changes (like improved insulin sensitivity) may take 4-8 weeks to become apparent. However, individual results vary greatly, and some people may not see benefits at all.

Want to Apply This Research?

  • Log your fasting schedule (when you eat and fast), energy levels (1-10 scale), hunger levels, and any physical symptoms daily. Track weight and measurements weekly. Note how you feel during and after fasting periods.
  • Start with a simple fasting schedule like 12-hour overnight fasting (eating between 8am-8pm, fasting 8pm-8am). Gradually adjust timing based on how you feel. Use the app to set reminders for eating and fasting windows, and track which schedule feels most sustainable for your lifestyle.
  • Review your logs monthly to identify patterns: Do certain fasting schedules improve your energy? Do you feel better on some days than others? Track consistency (how many days per week you stick to your plan) and correlate it with how you feel. Share data with your doctor at regular checkups to monitor for any health changes.

This review summarizes research on intermittent fasting but does not constitute medical advice. Intermittent fasting is not appropriate for everyone and may cause side effects in some people. Before starting intermittent fasting, consult with your healthcare provider, especially if you have diabetes, heart disease, thyroid conditions, take medications, are pregnant or breastfeeding, have a history of eating disorders, or have other health concerns. This research is based on a review of existing studies with significant limitations; larger, longer-term human studies are needed to establish safety and effectiveness. Individual results vary, and what works for one person may not work for another.