Do You Need Less Protein on Days That You Don’t Train

Protein, Muscles, Training and Protein Synthesis

Most bodybuilders know that on training days they need to up their protein intake to support increased recuperation and gains in lean muscle mass. The major goal of bodybuilding is to increase lean muscle mass. Requiring that muscle protein synthesis exceed protein breakdown over time.


Previous research shows that higher protein diets and resistance exercise have additive effects on lean body mass maintenance or even gain of lean body mass in caloric deficit. Higher protein diets and supplemental exercise tends to increase weight loss. But having greater effects on body composition through the preservation of lean body mass while increasing fat loss.

Protein Synthesis

how protein synthesis works
How muscles use protein to grow.

The muscle synthesis acute response from exercise is a dose response depending upon exercise intensity and work load. There is a delay in protein synthesis after exercise of about 45 minutes to an hour. Muscle protein synthesis rises sharply (2-3 fold) between 45 and 150 minutes.

The increased sensitivity of muscle protein synthesis in response to essential amino acid intake after exercise can last up to 24 hours. Some studies found resistance trained men consumed protein intakes of 1.8 to 2.7g/kg while engaged in extreme strength training programs.

Studies and Science

A new study set out to determine the protein needs of bodybuilders that had been training for three years on their “off” days. Some bodybuilders eat less protein on their “off” days, but this may be a mistake. The aforementioned study had bodybuilders tested 48 hours after their last bout of resistance exercise.

Then fed various doses of protein on their days they were resting. Shockingly, the study found that despite the bodybuilders not training, they had a high protein requirement on non-training days. Also demonstrated protein intake remains elevated at least 48 hours post workout.

You Should Consume Protein on Training and Non Training Days

The average protein requirement found 1.7 to 2.2g/kg per day. Even though they did not train for two whole days. Meaning, even though you may not be training on a certain day, muscle recovery and building still occurs as a result of your previous workout.

Choosing The Best Protein Supplement for Protein Synthesis


Whey is one of the most popular protein products on the market. It’s a milk-based protein that’s quickly digested and easily absorbed by your body, making it the perfect choice around your workouts. Whey protein is considered a complete protein, as it contains all nine essential amino acids necessary for optimal health.

It’s particularly high in the amino acid leucine, which turns on processes in your body involved in building muscle. Owing to its high leucine content and quick digestion, whey protein increases muscle protein synthesis — the process by which your muscles grow — more than other types of protein, specifically casein and soy.

Several meta-analyses show that whey protein supplements significantly increase muscle size and strength when combined with resistance training. Whey protein also promotes feelings of fullness, which can help you lose fat by eating less throughout the day.

Additionally, whey protein spares the loss of lean muscle mass during calorie restriction, especially when combined with exercise. This is important because your body tends to lose lean muscle mass along with body fat when you diet.


protein synthesis
Choosing the right protein for you.

Like whey, casein is a milk-based protein that contains all the essential amino acids your body needs. However, your body digests casein protein much slower than the rapidly digested whey protein. This is because casein forms curds in your stomach once exposed to stomach acid.

These curds are not easily broken apart and take your body much longer to digest and absorb. But because your body absorbs casein protein at a slower rate, it provides your muscles with a steady supply of amino acids over a longer period — usually between five and seven hours.

While casein protein doesn’t increase muscle protein synthesis to the same extent as whey, the continuous supply of amino acids helps prevent muscle breakdown and supports muscle protein synthesis longer. This makes casein protein particularly useful for promoting muscle growth during fasting, for example before sleep or between meals.

Studies in men show that consuming 20–30 grams of casein protein before bed decreases muscle protein breakdown and supports muscle building. And because aging is associated with a loss of muscle mass, older men may especially benefit from the muscle-preserving effects of casein protein.

Whey-Casein Blend

Whey-casein protein blends combine the fast- and slow-digesting properties of whey and casein protein powder. With a whey-casein blend, you get the best of both worlds: a spike in muscle protein synthesis from the rapidly-absorbed whey and a prolonged decrease in muscle breakdown from the slowly-absorbed casein.

In one study, 16 men at rest drank 20 grams of whey protein blend or 20 grams of whey-casein protein blend. The researchers took muscle samples from the men two hours before and several hours after consumption and found no difference between the two groups in muscle protein synthesis, suggesting the blend is just as effective as whey protein when resting.

However, it’s unclear if protein blends are as effective as whey protein for increasing muscle protein synthesis around exercise.

In a ten-week study, 68 men received whey-casein protein blend or an equal amount of casein protein while undergoing lower-body resistance training. Results showed that those consuming the whey-casein blend experienced less muscle fatigue compared to the casein group.

Still, no differences in muscle size or strength were detected between the two groups. The percentage of protein from whey and casein varies between products on the market. More often than not, the whey-casein blends contain more whey than casein.

In Conclusion

With the abundance of protein powders on the market, you may be wondering which one is best for you. If you can tolerate dairy, whey, casein and whey-casein blends are the best options for losing fat and gaining muscle. However, if you can’t tolerate dairy or if you follow a vegan diet, plant-based proteins like soy, pea and rice are the best protein sources.

For the best results, make sure to consume enough protein throughout the day and exercise at least three times per week. Adding muscle building supplements also helps with building muscle and strength gains.