Intermittent Fasting Schedule: 6 Plans With Clocks

Intermittent Fasting Schedule: 6 Plans With Clocks

Six common intermittent fasting schedules exist: 14:10, 16:8, 18:6, OMAD (20:4), 5:2, and alternate-day fasting. They differ in how long and how often you stop eating. Randomized trials found most of them roughly equal to plain calorie restriction for weight loss, so the schedule that works best is the one you can actually maintain.

The National Institute on Aging puts it plainly: "In short, there's not enough evidence to recommend any such eating regimen to the public." That does not mean fasting is useless. It means choosing a plan based on your daily routine matters more than chasing one protocol's supposed edge over another.

Before You Start

Pick by lifestyle, not by theory. Every schedule below restricts when you eat. None of them automatically restricts how much you eat, and in the trials below, the time window on its own did not beat plain calorie restriction. Before choosing:

• Know your anchor meals. If dinner with family is non-negotiable at 7 pm, an early 18:6 window that closes at 3 pm will not survive the week.
• Set a caffeine cutoff by bedtime, not by your eating window. Black coffee and plain tea are the usual fasting-window drinks, but a 2013 study (Drake et al., J Clin Sleep Med) found that 400 mg caffeine taken six hours before bed still disrupted sleep compared with placebo. An eight-hour buffer before lights-out is a reasonable margin. For an 11 pm bedtime, that means no caffeine after 3 pm, regardless of which plan you pick.
• Talk to your doctor first if you take medications that must be taken with food, if you have diabetes, kidney disease, or heart conditions, or if you are pregnant or breastfeeding. More on this in the safety section below.

Intermittent Fasting Schedules at a Glance

Source: sample clocks are illustrative; the 16:8, early 16:8, 18:6, 5:2, and alternate-day rows use the windows or energy targets from the trials cited below. The caffeine column is the same across every row because caffeine timing follows bedtime, not the eating window.

How to Pick a Schedule

1. Start gentle. A 12:12 or 14:10 split (stop eating after dinner, eat breakfast on time) is a common first step. Run it for a week to see how your energy and sleep respond before narrowing the window.
2. Fit the window around your life. Place the eating window where your social meals and your workouts fall. Forcing an early window when you train at 6 pm creates a conflict you will eventually drop.
3. Consider early windows if metabolic markers matter to you. A small crossover trial by Sutton et al. (2018, Cell Metab) found that a 6-hour early eating window (dinner before 3 pm) improved insulin sensitivity, blood pressure, and oxidative stress in men with prediabetes, independent of weight change.
4. Protect lean mass. The TREAT trial (Lowe et al., 2020) saw a larger loss of appendicular lean mass index in the 16:8 group than in the regular-meal group. Keep protein and total intake adequate whichever schedule you pick.
5. Reassess after four weeks. If adherence is slipping or energy is dropping, widen the window rather than pushing through.

Does 16:8 Work Better Than Eating Less?

In three randomized trials, 16:8 eating did not beat ordinary calorie restriction or regular meal timing for weight loss, though it beat a no-change control group.

• TREAT (Lowe et al., 2020, JAMA Intern Med): 116 adults with overweight or obesity, 12 weeks. The 16:8 group (noon to 8 pm, no calorie target) lost 0.94 kg; the consistent-meal-timing group lost 0.68 kg. No significant difference between groups.
• Lin et al., 2023 (Ann Intern Med): 90 adults with obesity, 12 months. The 16:8 group lost 4.61 kg more than a 10+ hour control, but the difference versus a 25% calorie-restriction group was 0.81 kg (P = 0.68), not significant.
• Liu et al., 2022 (NEJM): 139 adults with obesity, 12 months. An early 16:8 window (8 am to 4 pm) plus calorie restriction produced 8.0 kg of weight loss versus 6.3 kg with calorie restriction alone. The 1.8 kg gap was not significant (P = 0.11).

The pattern: 16:8 beat doing nothing, but it did not outperform the same calorie restriction done with regular meals.

What the Trials Found, Schedule by Schedule

Source: PubMed abstracts linked in Sources. Weight changes are each trial's own reported numbers.

Is 18:6 or OMAD Better Than 16:8?

Not proven. The Sutton 2018 crossover showed metabolic improvements with an early 6-hour window, but those benefits came from the timing (early eating) and were independent of weight loss, so they do not tell you that 18:6 beats 16:8 in general.

OMAD had a mixed signal. Stote et al. (2007) found less fat mass with one meal per day versus three, but also more hunger, higher blood pressure, and higher total and LDL cholesterol. A narrower window is not automatically better.

5:2 vs Alternate-Day Fasting

Both produced weight loss roughly equal to daily calorie restriction. Harvie et al. (2011) compared a 5:2-style plan (about 650 kcal on two days per week) with continuous 25% restriction in 107 premenopausal women over six months: weight loss was 6.4 kg versus 5.6 kg (P = 0.4), with a modestly larger drop in insulin resistance in the 5:2 group.

Trepanowski et al. (2017) tested alternate-day fasting (25% of energy needs on fast days, 125% on feed days) against daily restriction in 100 adults over 12 months. Weight loss was similar, but the alternate-day group had the highest dropout rate (38% versus 29% for daily restriction) and LDL cholesterol 11.5 mg/dL higher than the daily-restriction group at 12 months. The authors concluded alternate-day fasting offered no advantage in adherence, weight loss, or cardiovascular protection.

Where Coffee and Caffeine Fit a Fasting Schedule

Black coffee and plain tea contain negligible calories and are the usual fasting-window drinks (more detail in what you can have while fasting and does coffee break a fast). Plain black coffee and tea are generally treated as fine during a fast.

The limit that actually matters is sleep. Drake et al. found 400 mg caffeine six hours before bed still disrupted sleep versus placebo, so building in an eight-hour buffer before your usual bedtime is a safer margin. The FDA has cited 400 mg of caffeine a day as an amount not generally associated with negative effects for most adults.

For a closer look at whether a zero-sugar caffeine pouch (Roon contains sucralose) counts as breaking a fast, see do Roon pouches break a fast. And for more on how long caffeine lasts, that page covers half-life and clearance in detail.

Troubleshooting the First Two Weeks

• Tiredness mid-morning. Common while your body adjusts. Make sure you are sleeping enough, hydrating, and getting adequate electrolytes. More on why fasting makes you tired.
• Headaches. Drink water through the day and keep your usual caffeine timing steady rather than delaying it to match the eating window.
• Cream in your coffee. A splash of cream adds calories and technically breaks a strict fast. If you want a strict fast, keep it black. See dirty fasting vs clean fasting.
• Shifting the window on weekends. No trial tested weekend flexibility. A consistent window likely helps adherence, but a one- to two-hour shift for a Saturday brunch is a practical reality for most people.

Who Should Not Start Fasting Without a Clinician

This section is not optional reading. For some groups, changing when you eat carries real risks.

• Diabetes treated with insulin or glucose-lowering drugs. A randomized trial by Corley et al. (2018) found fasting more than doubled hypoglycemia risk (RR 2.05) in adults with type 2 diabetes on these medications, even after medication doses were reduced. Grajower and Horne (2019) noted that medical guidelines for intermittent fasting with diabetes are non-existent, and that with provider supervision and glucose monitoring it can be done safely.
• History of an eating disorder, or teenagers. A cross-sectional study of Canadian adolescents and young adults (Ganson et al., 2022) found intermittent fasting was associated with eating disorder psychopathology. Association is not causation, but the overlap warrants clinical guidance.
• Pregnancy or breastfeeding. Talk to your provider before changing when or how much you eat.
• Kidney disease or heart conditions. MedlinePlus states fasting "is not safe for everyone, especially those with health conditions like diabetes, kidney disease, or heart-related issues."
• Anyone on medicines that must be taken with food. Ask your doctor or pharmacist how a fasting window fits your dosing schedule.

Talk to your doctor before you change when you eat.

Related from Roon

• What Breaks a Fast? A Complete Guide
• Does Coffee Break a Fast?
• Intermittent Fasting and Focus: Where Ketones Fit

Frequently Asked Questions

Is 12 hours of fasting enough to count?

A 12:12 split is the gentlest common version of time-restricted eating. None of the trials cited above tested a 12-hour fasting window; the daily-window trials used 16 or 18 hours, and the others tested whole-day energy restriction. So there is no trial result here for 12:12 either way.

Can I switch schedules on weekends?

No trial has tested a mixed weekly schedule. In the TREAT trial, participants maintained the same noon-to-8 pm window daily. A consistent window is simpler to keep up, and an occasional shift of an hour or two for a weekend meal is a practical call no trial here addresses.

Does sleeping count toward the fast?

Yes. The fasting stretch is clock time, including sleep. That is what makes overnight fasting the backbone of every schedule above. A 16:8 plan where you stop eating at 8 pm and sleep from 11 pm to 7 am already covers 11 of the 16 fasting hours while you are asleep.

Which intermittent fasting schedule is best for beginners?

No head-to-head trial has compared schedules specifically in beginners. A 14:10 window or a later 16:8 (noon to 8 pm) tends to be the easiest fit for most daily routines because it skips or delays breakfast without cutting into dinner. Check the safety section above before starting, especially if you take medication or have any of the listed conditions.

A Steadier Fasted Morning

Roon is a zero-sugar caffeine pouch (80 mg caffeine, 60 mg L-theanine, 25 mg methylliberine, 5 mg theacrine) designed for a longer, steadier curve rather than a taller peak. Methylliberine slows how the body clears caffeine: a randomized, double-blind crossover pharmacokinetic study (n = 12) found co-administration with caffeine cut oral clearance from 41.9 to 17.1 L/hr and extended caffeine's half-life from 7.2 to 15 hours, with no increase in peak concentration (study). That study used 100 mg methylliberine and 150 mg caffeine, about 4x the methylliberine and 1.9x the caffeine in a single Roon pouch, so the direction of the effect applies but the exact numbers do not. A 15-hour half-life describes clearance, not 15 hours of noticeable effect; one pouch is typically felt for about 6 to 8 hours.

Roon contains sucralose (see does Roon break a fast for the full breakdown). Cap your day at four pouches and 400 mg caffeine from all sources, and finish your last one at least eight hours before you plan to sleep. Pricing starts from $9.16 per tin on a 12-tin subscription. Roon is a caffeine pouch, not a fasting supplement or a meal replacement.

Sources

• Lowe DA et al., JAMA Intern Med 2020;180(11):1491-1499. PubMed
• Liu D et al., NEJM 2022;386:1495-1504. PubMed
• Lin S et al., Ann Intern Med 2023;176(7):885-895. PubMed
• Sutton EF et al., Cell Metab 2018;27(6):1212-1221. PubMed
• Stote KS et al., Am J Clin Nutr 2007;85(4):981-8. PubMed
• Harvie MN et al., Int J Obes 2011;35(5):714-27. PubMed
• Trepanowski JF et al., JAMA Intern Med 2017;177(7):930-938. PubMed
• Corley BT et al., Diabet Med 2018;35(5):588-594. PubMed
• Grajower MM, Horne BD, Nutrients 2019;11(4):873. PubMed
• Ganson KT et al., Eat Behav 2022;47:101681. PubMed
• Drake C et al., J Clin Sleep Med 2013;9(11):1195-1200. PubMed
• NIA, "Calorie Restriction and Fasting Diets: What Do We Know?" NIA
• MedlinePlus, "5 Questions About Intermittent Fasting." MedlinePlus
• FDA, "Spilling the Beans: How Much Caffeine Is Too Much?" FDA

Written by Roon Team