The "anabolic window": does protein timing matter?

No. You don't need a protein shake within 30 minutes of training. In training studies that ran for weeks, protein eaten just before or after a workout made no clear difference to muscle. That held once total daily protein was counted.^[1][2] The daily total is what to get right: about 1.6 g per kg of body weight.^[3] Spread it over three to five meals or snacks.

The "anabolic window" is the idea that protein must arrive within a short spell around training. Miss it, and part of the workout goes to waste, or so the idea goes. (Anabolic means building up.) It sounds precise. The training studies tell a duller story.

If you haven't set your daily number yet, start with how much protein you need. This article is about when to eat it.

Why the clock matters less than the total

Once your daily total is right, timing seems to matter little.^[1][2] One risk is a swap. You rush a shake after training and feel done, but the day's total still falls short.

Many older timing studies also had a hidden problem. In the studies that didn't match total protein, the comparison groups ate about 1.33 g per kg a day. The timing groups ate about 1.66 g.^[1] So the "timing" group often just ate more protein. That makes it hard to tell a timing effect from an amount effect.

What the research says

Two kinds of studies show up in this topic, and they answer different questions.

• Lab studies measure muscle protein synthesis (how fast the body builds new muscle protein) for a few hours after one meal or one workout.
• Training studies measure muscle and strength over weeks or months.

Lab studies help explain why. Training studies tell you what to do. When they seem to disagree, the training studies win.

A meta-analysis pools the results of many studies on the same question into one estimate. An RCT (randomised controlled trial) puts people into groups by chance, so the groups start out alike.

Before or after training: about the same

A 2013 meta-analysis pooled 23 studies with 525 people to ask whether protein close to training builds more muscle.^[1] "Close" meant within about an hour before or after.^[1] Most participants were young and new to lifting.^[1]

At first glance, protein near training looked a little better for muscle, but not for strength.^[1] Then the authors accounted for how much protein people ate across the whole day. The studies could no longer detect a difference for muscle or for strength. Total daily protein was the strongest predictor of muscle growth.^[1]

There's a catch. Only 3 of the studies matched total protein between the groups, and 2 of those 3 found no benefit from timing.^[1] The authors said that small number limits firm conclusions.^[1] They added that if a window exists at all, it looks wider than an hour before and after training.^[1]

A 2025 meta-analysis took a narrower approach. It only included RCTs where one group had protein before each workout and the other had the same protein after, for at least four weeks. Five trials made the cut.^[2] Lean mass changed about the same either way.^[2] Lean mass means everything in your body that isn't fat: muscle, but also water, organs and bone. The authors rated the certainty of this evidence as low to very low.^[2] Limited evidence on its own: few trials, all small.

One result leaned the other way. Leg-press strength rose more when protein came before training. But that came from only 2 small trials. The authors rated it very low certainty and said more research is needed.^[2] Chest-press strength didn't differ.^[2] Note the direction: before, not after. Nothing here supports racing to drink a shake once you rack the bar.

A position stand is a group of experts summing up the research for a professional body. The International Society of Sports Nutrition (ISSN) says a workout's effect on muscle building lasts at least 24 hours, though it likely fades with time.^[4] Several of the position stand's authors declare industry ties.^[4] Expert consensus. This is the panel's view, not a tested finding.

A 2024 analysis of 116 RCTs with 4,711 people looked at it differently.^[5] It compared protein at different times of day against a placebo (a dummy drink with no protein). Against placebo, protein after exercise added about 0.5 kg of fat-free mass (close to lean mass). Protein at night added about 12 kg to the leg press.^[5] These numbers compare each time with a placebo, not one time with another. The authors still named the hours around training, and night, as key times. But they called for trials that compare timings directly.^[5] Mixed evidence.

Spreading protein over the day

Here the lab and the training studies give different answers.

In one lab study, 24 trained young men had 80 g of whey (a milk protein) over the 12 hours after a workout. One group had 10 g every 90 minutes. Another had 20 g every 3 hours. A third had 40 g every 6 hours.^[6] The 20 g every 3 hours group had the highest muscle protein synthesis.^[6]

Another lab study pulls the other way. In 36 young men, a single 100 g serving after a workout gave a bigger response than 25 g. And the response was still going after 12 hours.^[7] A big meal isn't wasted. That isn't advice to eat 100 g at once.

Neither study measured muscle growth. Both used only men and one workout. Mixed evidence: the lab studies disagree about the best pattern.

The training studies are few and small.

• Even meals, 12 weeks. In one trial, 26 young men lifted three times a week. One group spread its protein more evenly, with more at breakfast. The other ate a lot of it at dinner.^[8] The even group gained 2.5 kg of lean mass, against 1.8 kg.^[8] But the result fell just short of statistical significance (P = 0.06), so it's a hint, not a finding.^[8] By week 12, the even group was also eating a little less protein in total: 1.30 against 1.45 g per kg a day.^[8]
• Even or skewed, 16 weeks. In another trial, 41 men and women with a high body weight (average BMI 31.5, in the obesity range) dieted and lifted three days a week.^[9] Everyone ate 90 g of protein a day, either 30 g at each meal or 10 g, 20 g and 60 g.^[9] Lean mass and fat changed about the same in both groups.^[9] They ate about 1.0 g per kg a day.^[9] That's below the 1.4–2.0 g per kg the ISSN suggests for people who exercise.^[4]

So the two training trials don't agree. One found a hint of a benefit from spreading protein evenly; the other found none. Limited evidence. We only have a few small studies, so treat this as a best guess.

The ISSN suggests 20–40 g of protein per serving, spread evenly every 3–4 hours.^[4] Expert consensus.

If you train on an empty stomach

Training fasted means training with no meal in the hours before, such as first thing in the morning. A 2013 review pointed out that the window idea mostly assumes this setup.^[10]

Its authors suggest keeping the meals before and after training no more than about 3–4 hours apart. After a large mixed meal, they say 5–6 hours can be fine.^[10] Expert consensus. This is the authors' view, not a tested finding.

So if you lifted at 6 am on an empty stomach, last night's dinner was a long time ago. Eat a protein breakfast after the session rather than waiting for lunch.

Protein before bed

Does protein before bed help more than protein at other times? The evidence is thin.

In a 12-week trial, 44 young men lifted and drank either 27.5 g of protein or a placebo with no calories every night.^[11] The protein group gained more strength and more thigh muscle.^[11] The trial was partly funded by DSM, a company that makes food ingredients.^[11] But the placebo had no protein, so the protein group also got more protein in total.^[11] That means the study can't separate the timing from the extra protein. Limited evidence. One trial, young men only.

A 2025 trial in 30 older men, about 66 years old, tested 40 g of protein after training or before bed for 12 weeks. They already ate at least 1.0 g per kg a day.^[12] Muscle and strength rose in all groups, with no differences between them.^[12] Limited evidence: small groups, men only.

At most, a bedtime snack is a handy way to fit more protein into the day. If you want more on rest itself, see how much sleep matters for lifting.

How to time your protein

This is coaching practice, not a tested finding. It follows the evidence above, but nobody has tested this exact plan.

1. Set your daily total first. About 1.6 g per kg of body weight a day.
2. Split it into three to five meals or snacks. Give each a decent serving, roughly 20–40 g. If your day only allows two or three bigger meals, that's fine too.
3. Eat around training the way you'd eat anyway. A normal meal a few hours before and after covers it. Trained on an empty stomach? Have protein soon after.
4. Use a shake only if it's easier. A shake is a meal you can drink. Protein powder gets its own section in supplements with evidence.
5. Check your daily total for a week. That shows whether you're near your number or nowhere close. Tracking food covers how. If counting food makes you anxious, or you have a history of an eating disorder, skip the numbers and speak to a doctor or a registered dietitian.

Here's the sum for two people.

70 kg (about 154 lb), trains at 6 pm.

• Daily total: 70 × 1.6 = 112 g.
• Four servings of 28 g each make 112 g. So do 30 g at breakfast, lunch and dinner plus a 22 g snack.
• The 22 g snack at 4 pm, training at 6 pm, dinner at 7:30 pm. Snack and dinner sit three and a half hours apart, inside the review authors' 3–4 hour guide. No shake needed.

55 kg (about 121 lb), trains at 6 am before breakfast.

• Daily total: 55 × 1.6 = 88 g.
• Four servings of 22 g each make 88 g.
• Make breakfast, right after the session, one of those servings. Eggs, Greek yoghurt or a shake all work.

What's practical can differ from what looks neat on paper. If three big meals suit your day better than four smaller ones, eat three. The daily total is the part that showed up in the training studies.

Common mistakes

• Rushing a shake while the day falls short. The window story is old and sticky, so the shake feels urgent. Fix: get the daily total right first. Eat when it suits your day.
• Skipping protein because you "missed the window". People think the chance has gone, so why bother. Fix: eat your next meal as normal. A workout's effect lasts at least a day.^[4]
• Eating tiny servings every couple of hours. It sounds like it keeps muscle "fed". In the lab, 10 g every 90 minutes did worse than 20 g every 3 hours.^[6] Fix: eat normal meals with a decent serving each.
• Treating bedtime protein as magic. The young-men trial couldn't separate timing from the extra protein.^[11] Fix: count it as part of your daily total, nothing more.

How Gymbers fits

The step that matters here is the daily total. The Gymbers app logs protein, calories, carbs and fat against your daily targets. Find a food by searching the food database or scanning a barcode. Add your own foods too, like the shake you drink on the days a meal won't fit.