You’ve got your protein shake, dry-quick sweat towel, luxe yoga mat, dumbbells, resistance bands, fave Youtube trainer cued up and ready to tap play… but should you down that protein boost before you start your workout or save it for after?
Older advice about nutrient timing suggested that consuming protein within 30–60 minutes after finishing resistance exercise (aka the anabolic window) would result in greater gains in strength and muscle mass1.
Newer research questions the importance and even existence of a post-exercise window. So, what’s the best thing to do?
Let’s take a step back and look at the basics of protein. One of the three macronutrients (along with carbohydrates and fats), protein can be made by our bodies. Protein is made up of amino acids—there are 20 types of amino acids, 11 of which your body can synthesize, and nine that are essential to get from food.
We need protein to build and maintain muscles, make enzymes, transport molecules, provide cell structure… it plays a hand in just about every process in the body. If you don’t get enough protein, you could lose muscle mass, increase your risk of bone fractures, amplify your chance of infections, and inflate your appetite, among other things.
Protein release hormones (GLP-1 and CCK) that play a role in increasing satiety and decreasing levels of a hormone (neuropeptide Y) that can cause us to feel hungry.
You also burn more calories digesting protein than you do carbs or fat (called the thermic effect). Your body burns about 30 calories breaking down 100 calories of protein, whereas it uses about 10 calories to digest 100 calories of carbs and about 5 to digest the same calories of fat.
For these reasons, a meta-analysis of research showed persistent benefits of a higher-protein weight-loss diet on body weight and fat mass. The data from this analysis suggests that an effective higher-protein diet should contain between 1.2 grams to 1.6 grams of protein per kilogram of body weight and about 25–30 grams of protein per meal to provide improvements in appetite, weight management, and cardiometabolic risk factors2.
Researchers recommend that daily protein consumption be spread out, ideally four times a day. We need to eat protein throughout the day because, unlike carbs and fat, the body can’t store protein for quick use. Any excess protein you consume in one sitting will be oxidized for energy or converted into urine.
People, from vegans to carnivores, can defend their protein choices personally and loudly anywhere they can find a following. It’s the social media equivalent of rubber necking, where the crash may be spectacular but, in the aftermath, everyone is gobsmacked.
We’re not here to get into all that, but rather to provide some guidance on what high-quality protein means. Protein quality is determined by:
Proteins from animal sources, such as eggs, milk, meat, fish, poultry, provide the highest-quality rating of food sources, mostly because they’re “complete” proteins that contain all nine essential amino acids.
The highest-ranking protein sources3 that consider all three criteria above include:
Whey protein, which comes from cow’s milk, contain all essential and branched chain amino acids (BCAAs) and tends to be digested easily. Similar to whey, casein is derived from bovine milk and includes all essential amino acids.
Plant-based proteins can be combined to provide for all of the essential amino acids. Soy is the only plant source of protein that includes all essential amino acids as well as BCAAs to boot.
A review of studies published in the Journal of the International Society of Sports Nutrition recommends 0.4 grams of protein per kilogram of body weight per meal, which is about 20–30 grams4 to reach a daily amount of 1.6 g/kg.
A slightly higher daily protein intake of 1.75 g/kg/day showed moderate benefit in muscle strength and time trial performance5 compared to a daily intake of 1.2 g/kg in young endurance athletes.
If you want to build muscle, combine resistance training with daily protein consumption of 1.4 g/kg to 2 g/kg6; competitive bodybuilders likely need more protein than this, but direct research conducted on this population hasn’t revealed decisive recommendations.
For middle-aged and older adults, the current recommended daily amount7 to avoid deficiencies is 0.8 g/kg. One cross-sectional study showed that a daily protein intake of 1.02 g/kg was positively associated with the preservation of lean tissue8 in the arms and legs.
Powering up hills when you’re walking Fido or rounding out your booty with resistance band bridges and fire hydrants creates tiny tears in your muscles. Exercise initiates a protein remodeling stimulus by increasing muscle protein synthesis; eating protein after your workout optimizes the skeletal muscle adaptive response.
But… how soon after your workout should you sip that protein smoothie or eat a meal with about 25 grams of protein?
To recap, exercise creates tears in muscle tissue and it’s after the workout when muscle protein synthesis and autophagy9—cleaning out damaged cells to regenerate healthier ones—occurs to “make us stronger.”
The body uses protein during this rebuilding phase to repair the damaged tissues so it’s somewhat logical that you may guzzle a protein shake or eat a protein bar before you even wash the stench of sweat off in the shower.
That said, the classical post-exercise goal to reverse catabolic processes quickly for muscle recovery and growth may be applicable only if you started your workout without eating or drinking anything (besides water) first.
Consuming protein more immediately after finishing a strength training session could lead to cumulative gains in muscle mass if the workout was performed in a fasted state10.
Another study from 2017 tracked muscle strength, strength gains, and body composition changes in response to one group consuming 25 grams of protein (and 1 gram of carbs) immediately before and the other group immediately after. Both groups performed the same total-body exercises and reps. Results showed similar effects on all measures studied11 in both groups, supporting the idea that the post-exercise window may be several hours long.
The International Society of Sports Nutrition’s (ISSN) position on nutrient timing (published in 2017) states that exercisers should prioritize meeting the total daily intake of protein with evenly-spaced feedings of 25–40 grams to maximize muscle protein synthesis (MPS). Keep in mind that this is a slightly higher amount than the ranges listed earlier to account for sports nutrition needs for all levels, from occasional exercisers to competitive athletes.
While the ISSN states that post-exercise ingestion of high-quality protein sources either immediately or two hours after the workout stimulates a robust increase in MPS, it also cautions that the post-exercise protein feeding should be affected by the size and timing of a pre-exercise meal.
In short, ingesting 20–40 grams of high-quality protein every three to four hours12 affects MPS most favorably and is associated with improved body composition and performance outcomes compared to other fueling strategies.
Keep it simple and focus on your total daily protein intake instead of worrying about protein powders, blender bottles, and bars. If you eat the recommended amount every three to four hours, you’ll end up having enough protein at the right time for muscle repairs after you work out.