Intermittent Fasting by Age Chart | A Guide by Simple (2024)

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Intermittent Fasting by Age Chart | A Guide by Simple (1)

Writtenby Trey Reck

Medically reviewedby Josie Porter, RD

Intermittent Fasting by Age Chart | A Guide by Simple (3)

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    Intermittent fasting is an approach to eating that involves daily or weekly fasts (periods of time when you don’t eat) and has been linked to benefits like weight loss, supporting our immune function, reducing inflammation, and even supporting gut health.[1,2,3,4]

    You may have heard that you can determine your best intermittent fasting protocol by using your age. For instance, maybe it’s the case that 14-hour fasts work better for 30-somethings, whereas those who are 50+ would be better off doing 16:8.

    Intermittent Fasting by Age Chart | A Guide by Simple (4)

    Is there any truth in all this? Can you gauge the right intermittent fasting plan for you just by your age group? Let’s chart these waters and find out.

    Key takeaways

    • Intermittent fasting involves alternating between periods of eating and not eating (aka fasting).
    • Intermittent fasting can help you lose weight and benefit your health.
    • There’s no science to say that any intermittent fasting protocol works better at any specific age.
    • Some aspects of how our lives and bodies change over the years will influence the intermittent fasting plan that fits you best.
    Intermittent Fasting by Age Chart | A Guide by Simple (5)

    Intermittent fasting by age

    At SIMPLE, we like to keep things real and honest. So here’s the deal:

    there’s no scientific evidence to say what difference, if any, age makes to the effectiveness of fasting.

    Research on intermittent fasting has been carried out on all ages (yes, even centurions!), so it’s hard to say which schedule fits who best. What research does say, though, is that all sorts of fasting schedules are generally safe and effective for adults of all ages, so long as those adults are safe to fast.

    As the science isn’t there, we spoke to our expert team — who’ve worked with many fasters in both a clinical and research setting — to learn their firsthand experiences of which intermittent fasting plans worked better for different age groups and why.

    From their insights, we’ve put together some practical ideas about what to consider when choosing an intermittent fasting schedule according to your age.

    If you’re in the 18–30 age group

    Find an intermittent fasting plan that suits your social time

    Maybe it’s a game of beer pong with college pals, debriefing after work with colleagues over ramen, or spending Sunday evening discussing the latest episode of your fav show over some wine and cheese with friends — food and drink are an integral part of social life for many 18- to 30-year-olds.[5]

    If you’re at the social butterfly stage of life (whatever age you are, being social doesn’t have an age limit), choosing an intermittent fasting schedule you can adjust manually could be ideal, as you’re able to fit your fasting around your social time.

    For example, say you usually fast on an 18:6 plan. But this weekend you’re planning to hit late-night tacos with your workmates, then go into a big celebration for your best friend’s birthday. No worries! Switch to 14:10 to give yourself a longer eating window on these days, then flip back to 18:6 on Monday.

    You can mix it up as much as you need — your fasting window doesn’t have to be the same length every day to be effective.

    If you’re in the 30–45 age group

    Intermittent Fasting by Age Chart | A Guide by Simple (6)

    Find an intermittent fasting plan that fits your home / work life

    Maybe you got that promotion you were chasing in your 20s (congrats, btw!), and now, you’re juggling alllll the tasks: dinner with family, plus that last-minute task your boss sent you (thanks for that, boss), plus getting your work clothes dry-cleaned, plus staying up late to get some me-time, plus, plus, plus …

    Whew. It’s a lot.

    That busy lifestyle is a key factor when you’re finding an intermittent fasting schedule that works for you. Whichever fasting plan gives you sufficient time and space to eat and nourish that busy body and mind — without adding more stress to your life — that’s the winner.

    Perhaps 16:8 could be a good fit in general. Or maybe 14:10. Again, taking a manual approach where you flex your fasting window to fit the needs of your day will likely work best.

    Why not try our SIMPLE quiz, and use the app to get your fasting schedule set up? You’ll be able to control how long you fast each day, and it’ll help you keep track of where you’re at each day (that’s one less thing to remember!).

    If you’re in the 45–60 age group

    Find an intermittent fasting plan that supports menopause-related weight gain

    If you’re experiencing menopause-related weight gain, know that you are not alone. Many women are right there with you. It can be a tough time in life.

    Here’s the good news: intermittent fasting could help. Short-term studies show both pre- and post-menopausal women can lose fat with intermittent fasting plans like 18:6.[6]

    Other actions we’d suggest are:

    • making sure to eat enough protein
    • adding strength training to your weekly routine, if you can

    Both of these will help keep your muscles healthy, so you can stay strong and mobile.

    If you’re in the 60+ age group

    Choose an intermittent fasting plan that makes it easier to get all the nutrients you need

    As we get older (and hopefully wiser), we need extra nutrients — like protein, calcium, and vitamin D — to continue to thrive.[7,8]

    So if you’re intermittent fasting in this age group, err on the side of shorter fasts like 12:12, 14:10, or 16:8 to give yourself plenty of time to eat everything you need to look after your body.

    Again, exercise — all kinds, but especially strength training — can be a real bonus at this age too. (Truthfully, we’d suggest intermittent fasters of all ages to go get their lifting on!)

    An all-age-group note

    Taking medication?

    Of course, medication can be taken at any age. Yet we tend to use more medications as we get older.

    If you’re taking anything, be sure to check in with your doctor before starting any intermittent fasting plan, and continue taking them as prescribed (with food, on an empty stomach, etc.) even if you’re doing intermittent fasting.

    Intermittent fasting by gender

    Does intermittent fasting affect men and women differently?

    Because there are differences in how women’s bodies work compared to men’s — like hormones, the impact of calorie restriction, response to stress, etc. — women can experience intermittent fasting in ways that men don’t.

    This means that some women may respond well to gentler intermittent fasting plans and a slower introduction to fasting, like starting with 12:12 and working up to longer fasts over time.

    For a fuller breakdown, check out our guide on how intermittent fasting affects women.

    There are also social differences, and these can also come into play when thinking about which intermittent fasting plan to choose.

    For instance, women still tend to do more caregiving and may have to juggle their eating habits more around kids, animals, and wider family needs.[9] Men still tend to do more hours in the office, so they may need to juggle their eating times around meetings, long hours, and work trips.[10]

    Of course, these are generalizations, and typical gender roles may or may not factor into your approach to intermittent fasting. What matters is that you build your plans around your needs, whatever drives them.

    Intermittent fasting chart by age and gender

    Check out our intermittent fasting chart by age and gender to get a handy summary of everything we’ve just discussed.

    Intermittent Fasting by Age Chart | A Guide by Simple (7)

    How does intermittent fasting work?

    When you are intermittent fasting, your body goes from using glucose for energy to using stored fat. This is because your body needs a source of energy when you’re fasting since no glucose is coming in.

    It’s this metabolic shift, called ketosis, and the natural lowering of calories due to a shorter eating window that leads to weight loss and a lot of the health benefits intermittent fasting offers.

    Of course, intermittent fasting tends to work better if you work it. For a deep dive on kicking butt with intermittent fasting, here are your Must-Reads.

    • Learn what you can drink while fasting. (Spoiler alert: tea and coffee [without milk or sugar] and water are your friends.)
    • Get to grips with what to eat during intermittent fasting for goal-crushing nutrition. (Spoiler alert: vegetables and protein feature strongly.)
    • Build your how-to-meal-plan skills. (Spoiler alert: planning ahead makes your food choices better.)
    • Prepare for the most common intermittent fasting side effects. (Spoiler alert: feeling hungry and headaches are a couple.)
    • Bookmark this troubleshooting guide for those plateau moments when you’re not seeing results and it feels like intermittent fasting is not working. (Spoiler alert: sleep, eating enough, and getting active are in the mix.)

    Oh, and if you’re wondering, Does intermittent fasting slow metabolism? the answer is no. That consequence of calorie reduction doesn’t seem to happen so much with intermittent fasting.

    Intermittent Fasting by Age Chart | A Guide by Simple (8)

    The different types of intermittent fasting

    There are a number of intermittent fasting plans to choose from. This wide variety is one of intermittent fasting’s most winning features — there’s something for everyone.

    For the complete 411 on this, our intermittent fasting for beginners guide has you covered, but for the TL;DR version, read on!

    SIMPLE-approved

    Time-restricted eating

    Time-restricted eating can be done in lots of ways. Two solid options are:

    16:8

    Intermittent fasting on a 16:8 schedule means fasting for 16 hours and eating within an 8-hour window. Here, you can choose to either skip breakfast or have your evening meal a little earlier in the day. It all depends on what works best for you!

    18:6

    18:6 intermittent fasting is a type of time-restricted eating where you fast for 18 hours and eat within a 6-hour window each day.

    Other popular TRE methods include 12:12 and 14:10, and you can go off script here, too, to try something like 15:9 if it fits better! We are big fans of all TRE options up to and including 18:6.

    Medical approval recommended

    Intermittent Fasting by Age Chart | A Guide by Simple (9)

    The 5:2 diet

    The 5:2 diet involves eating normally for five days a week and restricting your calorie intake to 500–600 calories for two non-consecutive days in the week. While there is good evidence to support the use of 5:2, it should only be used in the SIMPLE app with the OK from your doctor.

    Alternate day fasting (ADF)

    Alternate day fasting is a type of intermittent fasting where you alternate between eating as normal one day and significantly reducing your calorie intake on the next. Science tells us that ADF can be super beneficial for weight loss. But, like 5:2, it should only be used in the SIMPLE app with your doctor’s sign of approval.

    20:4

    Intermittent fasting 20:4 is a type of time-restricted eating where you fast for 20 hours and eat within a 4-hour window each day. The thing is, while there are some studies looking at the weight loss benefits of 20:4, squeezing in all the nutrients you need in 4 hours is a tricky task (just ask our dietitians). Only use fasts longer than 18 hours with medical approval.

    Give these a pass

    Water fasting

    With water fasting, you consume only water for a specific period of time, typically ranging from 24 hours to several days or even weeks. This fasting method gets a no from us.

    OMAD

    The OMAD (One Meal a Day) diet involves eating only one meal per day, typically within a one-hour window, and fasting for the remaining 23 hours. It’s usually followed by really experienced fasters and something that we generally wouldn’t encourage the majority of you to follow.

    Eat Stop Eat

    Eat Stop Eat involves fasting for 24 hours once or twice a week, consuming no calories during the fast, and then returning to normal eating patterns. In our SIMPLE opinion, fasting for 24 hours is not superior to shorter fasts like 18:6 or 16:8, so why make your life harder than it has to be? Always check with your doctor if you plan on trying fasts longer than 18 hours.

    If this list has you feeling a little overwhelmed, why not try our SIMPLE quiz and let us take the load off your shoulders? We can give you a leg up by suggesting a fasting protocol based on what you tell us about yourself.

    Who shouldn’t try intermittent fasting?

    While intermittent fasting is generally safe and healthy for adults of all ages, some folk shouldn’t try it unless they have full permission and support from their doctor.

    That means you if you’re someone who:

    • is pregnant, breastfeeding, or trying to conceive
    • is under a lot of stress
    • has a Body Mass Index (BMI) lower than 18.5
    • is very active and/or has high daily energy demands
    • is under the age of 18, or 80 years old or more
    • has nutritional deficiencies
    • has a health condition, like diabetes or anemia
    • has (or is at risk of having) an eating disorder, or has a history of one
    • takes medications (especially those which affect blood glucose or blood pressure levels)

    Is intermittent fasting safe for kids?

    Sorry kiddos, intermittent fasting isn’t really recommended for you.[11]

    If you’re under 18, you’re still growing, so you need regular meals and snacks to get all the nutrients you need. Fasting can result in nutrient deficiencies that can impact your growth, development, energy levels, concentration, and overall well-being.

    While there is research in adolescents emerging [12], at SIMPLE we still think it’s too soon to tell if intermittent fasting is safe for children and teens.[13] So, for now, we’ll leave it to the pediatricians and pediatric specialist dietitians to decide what’s best.

    SIMPLE’s expert opinion and final thoughts

    Intermittent fasting is a fantastic tool for supporting your health and well-being. Not only can it help you lose weight and reduce your risk of various diseases [14], but it may also support your gut health and increase your concentration.[4]

    Trying to decide which intermittent fasting schedule to go for by your age group, on the other hand, is a pretty inexact science. After all, what makes sense for one 33-year-old may not make sense for another. The right intermittent fasting plan for you depends on you and your lifestyle, needs, and preferences. Your age and gender may or may not be factors in that.

    If you’re ready to give intermittent fasting a try, take our SIMPLE quiz, and start your fasting journey!

    Frequently Asked Questions

    What is the age limit for intermittent fasting?

    There is no strict upper age limit for intermittent fasting, but it’s not recommended for those under 18 or over 75, those who are pregnant or breastfeeding, those with eating disorders, or individuals with certain medical conditions.

    How long should a 40-year-old intermittent fast?

    How long a 40-year-old should intermittent fast for is up to them. Intermittent fasting is flexible, and the best schedule for anyone in their 40s depends on their preferences and lifestyle. They have the full suite to choose from, should they wish!

    Is intermittent fasting good for those over 50?

    Intermittent fasting can be good for those over 50.[15] It can help you be more mindful of food, combat menopause-related weight gain, and lower the risk of conditions like diabetes. Do make sure to chat with a doctor first if you have any medical conditions.

    Can a 70-year-old do intermittent fasting?

    Intermittent fasting can be done by 70-year-olds, but it’s important to approach it with caution and before making any decisions that may impact your health, always chat with your doctor.

    How many hours should a woman over 50 fast?

    How many hours a woman over 50 should fast is completely up to her and what she needs. Check out our ideas above.

    Intermittent Fasting by Age Chart | A Guide by Simple (10)

    1. Welton S, Minty R, O’Driscoll T, Willms H, Poirier D, Madden S, Kelly L. Intermittent fasting and weight loss: Systematic review. Canadian Family Physician. 2020 Feb 1;66(2):117-25.
    2. He Z, Xu H, Li C, Yang H, Mao Y. Intermittent fasting and immunomodulatory effects: A systematic review. Frontiers in Nutrition. 2023 Feb 28;10:269.
    3. Wang X, Yang Q, Liao Q, Li M, Zhang P, Santos HO, Kord-Varkaneh H, Abshirini M. Effects of intermittent fasting diets on plasma concentrations of inflammatory biomarkers: a systematic review and meta-analysis of randomized controlled trials. Nutrition. 2020 Nov 1;79:110974.
    4. Pérez‐Gerdel T, Camargo M, Alvarado M, Ramírez JD. Impact of Intermittent Fasting on the Gut Microbiota: A Systematic Review. Advanced Biology. 2023 Mar 22:2200337.
    5. Moutinho LS, Mendes AM, Lopes M. Alcohol Consumption and Binge Drinking Among Young Adults Aged 20–30 Years in Lisbon, Portugal. Journal of addictions nursing. 2018 Oct 1;29(4):E9-15.
    6. Cienfuegos S, Gabel K, Kalam F, Ezpeleta M, Lin S, Varady KA. Changes in body weight and metabolic risk during time restricted feeding in premenopausal versus postmenopausal women. Experimental Gerontology. 2021 Oct 15;154:111545.
    7. Deutz NEP, Bauer JM, Barazzoni R, Biolo G, Boirie Y, Bosy-Westphal A, et al. Protein intake and exercise for optimal muscle function with aging: recommendations from the ESPEN Expert Group. Clin Nutr. 2014 Dec;33(6):929–36.
    8. My Plate. U.S . Department of Agriculture. Older adults [Internet]. 2020-2025.
    9. Barger A., Best C. The State of Women and Caregiving [Internet]. Caregiving.Com. 2022 Feb.
    10. Doyle A. What are the average hours worked per week in the US? [Internet]. The Balance. 2022 Sep.
    11. Whyte HE, Findlay SM, Canadian Paediatric Society, Adolescent Health Committee. Dieting in adolescence. Paediatrics & Child Health. 2004 Sep 1;9(7):487-91.
    12. Jebeile H, Gow ML, Lister NB, Mosalman Haghighi M, Ayer J, Cowell CT, Baur LA, Garnett SP. Intermittent energy restriction is a feasible, effective, and acceptable intervention to treat adolescents with obesity. The Journal of Nutrition. 2019 Jul 1;149(7):1189-97.
    13. Ganson KT, Cuccolo K, Hallward L, Nagata JM. Intermittent fasting: Describing engagement and associations with eating disorder behaviors and psychopathology among Canadian adolescents and young adults. Eating Behaviors. 2022 Dec 1;47:101681.
    14. Abeyasekera KN. Benefits of Intermittent Fasting: A Systematic Review of Randomized Clinical Trials.
    15. Anton S, Ezzati A, Witt D, McLaren C, Vial P. The effects of intermittent fasting regimens in middle-age and older adults: Current state of evidence. Experimental Gerontology. 2021 Dec 1;156:111617.

    Intermittent Fasting

    Writtenby Trey Reck

    Medically reviewedby Josie Porter, RD

    Intermittent Fasting by Age Chart | A Guide by Simple (12)

    Intermittent Fasting by Age Chart | A Guide by Simple (2024)

    FAQs

    What is the best intermittent fasting schedule for my age? ›

    Understanding Intermittent Fasting by Age
    AGECONSIDERPOSSIBLE IF SCHEDULE
    30-45Your home and work routineEasy and simple schedules like 16:8 and 14:10
    45-60Weight gain due to menopauseWeight-loss promoting fasting periods like 18:6 and 16:8
    60+Types of nutrients you eatShort fast periods like 12:12, 14:10, 16:8
    1 more row
    Dec 3, 2023

    How many hours should a 70 year old fast? ›

    Many seniors benefit from this practice, with 16-8 intermittent fasting being the most popular option. This method necessitates an eight-hour window for eating and a sixteen-hour fast regularly, making it easier to stick to in the long run.

    What is the intermittent fasting schedule for seniors? ›

    This is the most popular type of IF. The daily method typically follows a 16/8 or 18/6 rule. That means eating regular, healthy foods during a 6- to 8-hour window each day, then fasting for the remaining 16 to 18 hours. Many people find this to to be the most sustainable way to fast.

    What is the best intermittent fasting schedule for beginners? ›

    A good option for beginners, then, is to fast for a set number of hours each day. This option allows you to start with fasting for around 12 hours a day, most of which you will be asleep. After you get more comfortable with 12-hour fasts, you can slowly lengthen the time of the fast.

    Which meal is best to skip for intermittent fasting? ›

    People who follow intermittent fasting either skip their breakfast or dinner, but experts say if the choice is between breakfast or dinner, one should choose to skip the latter.

    Does lemon water break a fast? ›

    Considering its low calorie content, plain lemon water will not break your fast in most cases. Yet, other lemon beverages may contain added sugar, so it's smart to read the food label to determine the calorie content. In addition, you should research the guidelines for your particular fasting approach.

    Does coffee break intermittent fasting? ›

    Technically speaking, eating or drinking any calories breaks a fast. That means it's generally considered OK to drink black, unsweetened coffee or tea, as well as water.

    Why is 16 hours the magic number for fasting? ›

    While both 12-hour and 16-hour fasting can promote fat burning, it's possible that a 16-hour fast may be more effective. This is because the longer fasting period may lead to a greater depletion of glycogen stores, which can trigger higher levels of fat burning.

    What is the best intermittent fasting window to lose belly fat? ›

    Depending on your lifestyle and when you can manage to stop eating, the best hours for intermittent fasting include the 16/8 or 14/10 fasting periods. Intermittent fasting is hailed by many as the new mantra of weight loss, disease prevention, and reversal of aging.

    What is the most popular intermittent fasting time? ›

    This form of fasting is a safer bet for many people who are interested in trying intermittent fasting for the first time,” says Zumpano. Some of the most common fasting windows are: The 16/8 method: Only eating between 10 a.m. and 6 p.m. The 14/10 method: Only eating between 9 a.m. and 7 p.m.

    What can you drink while intermittent fasting? ›

    What can I eat while intermittent fasting? During the times when you're not eating, water and zero-calorie beverages such as black coffee and tea are permitted.

    What is the best fasting schedule for longevity? ›

    Eating for 12 hours and then fasting for 12 hours is likely safe for most people, Longo explains. “That pattern of eating is very common among people who have record lifespans,” he says. “It seems to match both science and tradition.”

    What is the best first meal for intermittent fasting? ›

    Start your fast correctly: The best way is to have a low-carb meal, with healthy fats and high-quality protein. This allows your body to activate satiety hormones that have long-term effects and mean you won't experience hunger for a long time.

    What is the first meal of the day for intermittent fasting? ›

    You can start intermittent fasting by skipping breakfast, having your first meal in the afternoon (about 12 p.m.), and eating your last meal before 8 p.m. Intermittent fasting is a popular type of eating plan that involves fasting for a period of time between eating periods.

    What is the most aggressive intermittent fasting schedule? ›

    Alternate-Day Fasting (ADF) is one of the most aggressive intermittent fasting schedules.

    What are the best intermittent fasting hours for me? ›

    Depending on your lifestyle and when you can manage to stop eating, the best hours for intermittent fasting include the 16/8 or 14/10 fasting periods. Intermittent fasting is hailed by many as the new mantra of weight loss, disease prevention, and reversal of aging.

    How do I choose an intermittent fasting plan? ›

    The smart way to calibrate your fasting protocol is by easing into it. Start with a 12 hour fast and scale up from there until you find a program that works best for your body. Once you have established which IF protocol works best for you, you can then maintain this level, listen to your body, and adjust if needed.

    What is the best intermittent fasting interval for weight loss? ›

    A 2023 review of research found that the 16/8 method and 16/8 combined with restricting calories were effective strategies for weight control in adults with overweight or obesity. An eating window starting before noon led to greater weight loss than one that began after noon.

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