Somewhere along your weight loss journey, you may have heard that drinking a protein shake before bed will help you lose weight. Although protein before bedtime has been linked to increased metabolism the next morning, there's not enough research to say whether that effect translates to long-term weight loss.
But having protein before bedtime may increase your lean muscle mass and overall strength, if that's one of your goals.
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Protein promotes weight loss, but the jury's out on whether protein before bedtime increases metabolism. Having a protein shake at night may help grow muscles, though, and doesn't appear to have a negative effect, so there's probably no harm in trying it for yourself.
Protein Before Bed
Protein is often hailed as a weight loss-promoting nutrient because helps suppress appetite, increases metabolism and calories burned, increases muscle mass and decreases body fat. Because of these general weight-loss benefits, people often speculate that drinking a protein shake before bed can help boost weight loss even more.
However, when it comes to whether having a protein shake before bed will promote weight loss, the science is a little mixed. The idea came about due to a few (albeit small) studies whose findings were that having protein before bed can make your metabolism higher the next morning. Other studies, however, have shown no such effect. But studies on both sides had limitations.
Some studies gave participants a protein shake that was low in carbohydrates, while others combined protein with a moderate carbohydrate intake as well. Because these studies don't compare apples to apples (or protein shake to protein shake, in this case) it's not possible to make definitive statements about whether having a protein shake at night promotes weight loss.
However, based on the research, it does appear that it doesn't hurt to try, especially if the protein shakes don't take you over your calorie and macronutrient needs.
What the Science Says
One of the studies in favor of having protein before bedtime, which was published in Nutrients in September 2018, reported that women who consumed 48 grams of protein before bed had an increased resting metabolic rate (or RMR) in the morning. In other words, their metabolisms were faster in the morning and they were burning more calories, even without exercise. This effect was not seen with a lower intake of 24 grams of protein, which was measured in the same study.
Another similar study (with male subjects) published in a January 2014 issue of the British Journal of Nutrition found that men who were supplementing with protein 30 minutes before bed had a higher metabolism in the morning, but they experienced the same levels of hunger when compared to men given a placebo before bed. That means that, while metabolism may have been increased, it's likely that the men who supplemented with protein ate the same amount of food the next day as the men who didn't.
The Other Side
On the other hand, researchers from a study published in the British Journal of Nutrition in June 2018 reported that a protein-rich bedtime drink (in this case, milk) did not have an effect on metabolic rate or on the number of calories burned in males with overweight.
In this study, researchers gave men with overweight milk containing either 10 grams or 30 grams of protein 30 minutes before bed. The researchers found no positive changes in the men's metabolism or appetite the next morning with either dosage of protein. However, they did find that drinking the milk helped curb nighttime hunger, which may decrease the amount of snacking before bed.
It's important to note, though, that, in addition to protein, milk is also high in carbohydrates, specifically the sugar lactose, so it's possible that the carbohydrates had a negative impact on the metabolic rate and the number of calories burned due to the release of insulin.
Protein Shakes and Muscle Gain
Although drinking a protein shake before bed may not be enough to promote weight loss without considering other dietary and lifestyle factors, it may help increase muscle mass and boost strength. One small study published in the Journal of Nutrition in June 2015 found that, when combined with a 12-week resistance training program, having a protein shake at night helped increase muscle strength to a greater degree in men than going to bed without one.
Another small study published in Medicine and Science in Sports and Exercise in 2012 reported that men who drank a protein shake containing 20 grams of protein before bed, but after resistance training exercises, had better post-exercise recovery and muscle synthesis (or muscle growth) than when they didn't.
Although these studies specifically looked at muscle growth and not weight loss, they point to the possibility that drinking protein shakes before bed could promote weight loss too, since having more muscle mass helps you burn more calories at rest. Still, it's important to note that these studies combined protein before bedtime with a resistance training workout regimen. You likely won't be able to get these results without exercise by drinking protein shakes alone.
Choosing a Protein Shake
If you decide to drink a protein shake at night as part of your weight-loss regimen, the type of protein you choose may make a difference. According to an August 2016 report in Nutrients, casein protein, derived from milk, is the best choice before bed because it digests slowly and helps build muscle better than other forms of protein, like whey or pea.
It's also important to avoid protein shakes that have sugar. As some of the studies found, combining carbohydrates with protein may raise your insulin levels, promoting fat storage, and can negate any beneficial effects of consuming protein on its own. Look at the ingredients list on your protein shake and make sure it doesn't include sugar in any form. Unfortunately, sugar isn't always listed as "sugar," so watch out for ingredients like:
- Corn syrup
- Brown rice syrup
- Cane juice
- Golden syrup
- Fruit juice concentrate
- Maple syrup
- Raw sugar
- The Journal of Nutrition: "Protein Ingestion Before Sleep Increases Muscle Mass and Strength Gains During Prolonged Resistance-Type Exercise Training in Healthy Young Men"
- Medicine and Science in Sports and Exercise: "Protein Ingestion Before Sleep Improves Post-Exercise Overnight Recovery"
- Nutrients: "Pre-Sleep Consumption of Casein and Whey Protein: Effects on Morning Metabolism and Resistance Exercise Performance in Active Women"
- The British Journal of Nutrition: "A Bedtime Milk Snack Does Not Impact RMR, Substrate Utilisation and Appetite the Following Morning in Mildly Overweight Males"
- The British Journal of Nutrition: "Night-Time Consumption of Protein or Carbohydrate Results in Increased Morning Resting Energy Expenditure in Active College-Aged Men"
- The British Journal of Nutrition: "Influence of Night-Time Protein and Carbohydrate Intake on Appetite and Cardiometabolic Risk in Sedentary Overweight and Obese Women"
- Nutrients: "The Effect of Casein Protein Prior to Sleep on Fat Metabolism in Obese Men"
- University of California San Francisco: "Hidden in Plain Sight"