There is no official medical chart that sets fasting hours by age. What changes with age is what you need to fit into your eating window: more protein and more nutrients as you get older, and more room for a busy life in your 20s to 40s. The chart below is our starting point for each age group. It is a guide, not a prescription.
| Age | Starting schedule | Fasting / eating hours | Main focus |
|---|---|---|---|
| 18 to 30 | 16:8, or 18:6 once you’re used to it | 16 to 18 h fast, 6 to 8 h eating | A schedule that bends around social plans |
| 30 to 45 | 16:8 or 14:10 | 14 to 16 h fast, 8 to 10 h eating | Fitting fasting around work and family |
| 45 to 60 | 14:10 or 16:8; 5:2 or alternate-day fasting with a doctor’s OK | 14 to 16 h fast, 8 to 10 h eating | Weight gain around menopause, keeping muscle |
| 60 and above | 12:12 or 14:10 | 12 to 14 h fast, 10 to 12 h eating | Enough protein and nutrients every day |
Under 18? Don’t fast for weight loss without a doctor. Growing bodies need regular meals (see the section on children below). If you have diabetes, take medication, are pregnant or breastfeeding, or have a history of an eating disorder, talk to your doctor before you start at any age.
Below, we explain each age group, how men and women can respond differently, and who should avoid fasting.
What is Intermittent Fasting?
Intermittent Fasting (IF) involves alternating between eating and fasting periods. Integrating intermittent fasting into your regimen can help you shed weight quickly. It carries several other benefits, such as increased longevity, improved insulin sensitivity, heart health, etc. The different types of IF methods include:
- The 16:8 Method: This program includes calorie restriction for 16 hours and eating within an eight-hour window. This plan is incredibly flexible and easy to follow.
- The 5:2 Diet Method: In this method, you can eat normally for five days but must fast for two non-consecutive days in a week. During the fast, you must restrict yourself to 500-600 calories per day. [1][2]
- The Eat-Stop-Eat Method: It involves fasting for one entire day once or twice a week.
- The Alternate-Day Fasting Method: It includes fasting on every alternate day. However, you can have some calories up to a maximum of 25% or 500 calories per day during your fasting schedule. [3]
- OMAD (One Meal a Day): This fasting plan requires you to meet your daily caloric needs within a one-hour window and fast for the rest of the day. This is an extreme form of intermittent fasting. [4]
Intermittent Fasting Based on Age
Although intermittent fasting is an age-old practice, it has gained traction in the past decade. Several types of research have been conducted on intermittent fasting on people of every age, but it is difficult to come to a conclusion as to which type of fasting plan is suitable for whom. However, research indicates that most intermittent fasting plans are safe and tolerable for people of all ages. [5]
For the 18-30 Age Group
Whether it’s a night out with friends, discussing work-related issues with colleagues at the office, or enjoying a Sunday evening with family, eating and drinking are integral to people of the 18 to 30 age group.
If you love socializing, choosing an intermittent fasting plan will depend on your lifestyle. Let’s say you’re already following a 16/8 intermittent fasting (IF) plan, but something unexpected comes up. In such a scenario, you can adapt and transition to a 14/10 plan, giving yourself a slightly wider eating window. Return to your original 16/8 fasting plan after you are back on your regular routine. Case in point — you don’t always have to be strict on your schedule.
For the 30 to 45 Age Group
During the early 30s’ to mid-40s’ people usually juggle personal and professional commitments. Managing household chores, children, work obligations, and fulfilling societal commitments can be demanding.
Instead of getting overwhelmed, you must seek a fasting plan that suits your schedule and can help you manage your commitments effectively.
But which IF plan should you choose? Here’s the catch! You must choose an intermittent fasting plan that gels with your lifestyle. Choose the 16/8 or 14/10 plan, or create a customized fasting schedule that aligns with your daily schedule.
For the 45 to 60 Age Group
A major cause of weight gain in women between the ages of 45 to 55 is menopause. Weight gain is more prevalent in women than men at this age because women go through severe hormonal imbalances during this transition. [6]
Intermittent fasting can help some women going through menopause. In one study, alternate-day fasting (ADF) helped postmenopausal women lose about 5 to 6% of their body weight in 12 weeks, the same as premenopausal women and men (see our menopause diet plan). It is a demanding schedule, so try a daily window like 14:10 or 16:8 first, and talk to your doctor before you try ADF. [7]
However, while practicing IF, increasing protein intake, including strength training, having enough water, and avoiding snacking on unhealthy foods are essential. This approach helps you get the most out of intermittent fasting.
For the 60 and Above Age Group
With age, your body needs extra nutrients, such as proteins, vitamins, minerals, antioxidants, etc., to maintain well-being. When you enter this age bracket, shorter fasts like 12/12 or 14/10 are suitable because they allow ample time to eat well and meet your daily nutrient needs.
Exercise with intermittent fasting is an excellent approach. In fact, those who follow intermittent fasting should include physical activity in their daily regimen, irrespective of their age groups. After 60, strength training matters most, because it helps you hold on to muscle while you eat in a shorter window.
Intermittent Fasting Based on Gender
Men and women differ physiologically, which affects how intermittent fasting impacts each gender. Women may have a different experience with intermittent fasting than men due to their body composition, hormone levels, stress response, and calorie restriction approaches.
Some women may experience the benefits of intermittent fasting quicker than others that too on a milder fasting method. In contrast, some women find it difficult to reap the benefits of IF even with a more extended fasting protocol.
Men often find longer fasting windows easier to stick to, but the research on how fasting affects men and women differently is still limited. Start with a shorter window, watch your energy, sleep, and (for women) your cycle, and lengthen it only if you feel well. [8]
Is Intermittent Fasting Safe for Children?
Children and teenagers should not do intermittent fasting since, at this age, their body requires a lot of nutrients to grow. With intermittent fasting, fulfilling all the nutritional needs may not be possible due to the long fasting hours. Restricting the diets of young children may adversely hamper their growth, development, energy levels, and mental well-being.
If your child is overweight, don’t put them on a fasting schedule. Work with your pediatrician on regular, structured meals instead. These habits help:
- Ensure your child has food at defined intervals.
- Provide specific instructions about meal portions and snacking times.
- Eliminate all the sugary drinks from the kid’s diet.
- Prepare nutritious food with varieties to allure your kid. It should contain low-carb fruits, plenty of vegetables, lean proteins, and healthy fats.
- Convince your child to stay away from junk food. If it sounds challenging, then start limiting them gradually.
- Encourage your child to have their meal at the dinner table with family, not in front of their gadgets.
- Most importantly, consult your doctor and regularly monitor your child’s progress.
How Does Intermittent Fasting Work?
During a fast, your insulin levels fall and your body first burns its stored glucose (glycogen). As those stores run low, usually after 12 hours or more, it burns more fat and starts making ketones. That shift is called ketosis. Most of the weight loss from intermittent fasting still comes from eating fewer calories overall. [9]
Here are some tips to help you avail the maximum benefits of intermittent fasting.
- Abstain from eating anything during the fasting window. However, you can enjoy water, tea, and coffee without milk and sugar.
- Emphasize low-carb fruits and enough veggies.
- Your meals should incorporate lean proteins, dietary fibers, low-fat dairy, fruits, vegetables, and healthy fats.
- Drink plenty of water.
- Eat mindfully during the eating window.
- Exercise.
Who Should Avoid Intermittent Fasting?
Although intermittent fasting is considered safe for all adults, people with the following health conditions should refrain from trying it unless advised by a registered medical practitioner:
- Minors
- Women trying to conceive
- Pregnant or breastfeeding women
- Low BMI (below 18.5)
- Highly active individuals
- Underweight people
- Have health issues like diabetes and anemia
- Immunocompromised people
- Folks dealing with eating disorders
- People on certain medications that cannot be taken on an empty stomach
Frequently Asked Questions
What is the best age for intermittent fasting?
There is no single best age. Healthy adults of most ages can try it, starting with a gentler schedule as they get older (see the chart above). It is not recommended under 18. Older adults, pregnant and breastfeeding women, people with eating disorders, and anyone with a medical condition should get a doctor’s clearance first.
How is intermittent fasting done at 40?
At the age of 40 or above, people are usually predisposed to lifestyle diseases such as diabetes, high blood pressure, and cardiac issues. Among the various IF methods, the 16:8 method is a highly adaptable fasting technique that works best for people over 40.
Can a 16-year-old do intermittent fasting?
It is not advisable to practice intermittent fasting at the age of 16. This is because prolonged fasts can make meeting all your nutritional requirements challenging. Furthermore, calorie restriction may impede your physical and mental well-being and adversely affect your energy levels.
However, an intentional eating approach with workouts may work wonders if you are overweight and wish to shed extra pounds.
Is it better to fast for 12 or 16 hours?
As per research, although fasting has many health benefits, doing it for extended hours may have a higher risk of developing health concerns like gallbladder stones. However, a 12:12 approach is likely safe for most. [10]
Wrapping Up
Over the years, intermittent fasting has gained popularity due to its various health benefits. However, different fasting patterns are recommended for different age groups. While young adults may experience weight loss, improved insulin sensitivity, and metabolic health by following an IF plan, older adults may benefit from increased longevity, reduced inflammation, and improved cognitive function.
However, the impact of intermittent fasting can vary from person to person depending on factors such as genetics, stress levels, health issues, and lifestyle. The IF age chart provided in this article can help you get started with intermittent fasting.
References
Fitness Volt is committed to providing our readers with science-based information. We use only credible and peer-reviewed sources to support the information we share in our articles.
- Patterson, R. E., Laughlin, G. A., Sears, D. D., LaCroix, A. Z., Marinac, C., Gallo, L. C., Hartman, S. J., Natarajan, L., Senger, C. M., Martínez, M. E., & Villaseñor, A. (2015, April 6). INTERMITTENT FASTING AND HUMAN METABOLIC HEALTH. PubMed Central (PMC). https://doi.org/10.1016/j.jand.2015.02.018
- Welton, S., Minty, R., O’Driscoll, T., Willms, H., Poirier, D., Madden, S., & Kelly, L. (n.d.). Intermittent fasting and weight loss: Systematic review. PubMed Central (PMC). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7021351/
- Cui, Y., Cai, T., Zhou, Z., Mu, Y., Lu, Y., Gao, Z., Wu, J., & Zhang, Y. (2020, November 24). Health Effects of Alternate-Day Fasting in Adults: A Systematic Review and Meta-Analysis. PubMed Central (PMC). https://doi.org/10.3389/fnut.2020.586036
- Parveen, S., & Alhazmi, Y. A. (2022, November 5). Impact of Intermittent Fasting on Metabolic Syndrome and Periodontal Disease—A Suggested Preventive Strategy to Reduce the Public Health Burden. PubMed Central (PMC). https://doi.org/10.3390/ijerph192114536
- Rynders, C. A., Thomas, E. A., Zaman, A., Pan, Z., Catenacci, V. A., & Melanson, E. L. (2019, October 14). Effectiveness of Intermittent Fasting and Time-Restricted Feeding Compared to Continuous Energy Restriction for Weight Loss. PubMed Central (PMC). https://doi.org/10.3390/nu11102442
- Knight, M. G., Anekwe, C., Washington, K., Akam, E. Y., Wang, E., & Stanford, F. C. (2021, May 24). Weight Regulation in Menopause. PubMed Central (PMC). https://doi.org/10.1097/GME.0000000000001792
- Lin, S., Oliveira, M. L., Gabel, K., Kalam, F., Cienfuegos, S., Ezpeleta, M., Bhutani, S., & Varady, K. A. (2020, October 31). Does the weight loss efficacy of alternate-day fasting differ according to sex and menopausal status? PubMed Central (PMC). https://doi.org/10.1016/j.numecd.2020.10.018
- Mattson, M. P., Longo, V. D., & Harvie, M. (2016, October 31). Impact of intermittent fasting on health and disease processes. PubMed Central (PMC). https://doi.org/10.1016/j.arr.2016.10.005
- Welton, S., Minty, R., O’Driscoll, T., Willms, H., Poirier, D., Madden, S., & Kelly, L. (n.d.). Intermittent fasting and weight loss: Systematic review. PubMed Central (PMC). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7021351/
- To Fast or Not to Fast. (2019, November 22). NIH News in Health. https://newsinhealth.nih.gov/2019/12/fast-or-not-fast
