If your goal is weight gain, milk may be able to help you do the trick. Of course, it's not the answer all on its own; but when you combine milk with increased overall calorie intake, the proteins in the milk may help make weight gain, specifically in the form of lean muscle, easier.
However, if you simply increase your calorie intake without incorporating resistance training, there's really no way to control how that weight is stored. In other words, without exercise, it's possible that drinking milk at night will make you fat, not increase your muscle mass.
Milk Before Bed — The Benefits
Milk contains two highly digestible and absorbable proteins: casein and whey. Although whey gets a lot of attention in the supplement world, casein is actually the more abundant protein, comprising around 80 percent of milk's protein content. Although there are only a few studies that measured the effect of nighttime milk consumption on body composition, there are some promising results.
One study, published in the International Journal of Exercise Science in May 2017, looked at the effects of consuming casein at night and found that when taken right before bed, casein produced a more favorable anabolic response and better protein synthesis than when taken earlier in the day. In other words, the casein helped participants increase lean muscle mass while they were sleeping.
Another review, published in a September 2018 issue of Nutrients, looked at the effects of milk proteins on metabolic rate. The people in charge of the study reviewed available research and reported that when taken about 30 minutes before bedtime, both whey and casein can increase overnight muscle protein synthesis.
However, the report also noted that, in addition to increasing protein synthesis, milk can increase your morning resting metabolic rate (or the amount of calories you burn doing nothing). That means that milk may actually help you lose weight, instead of making you gain it.
The Other Side of Milk
A report published in the International Journal of Obesity in January 2012 backed up these findings, noting that people with a high consumption of dairy products tend to have greater weight loss and reduced risk of obesity compared to people with lower consumption.
However, the report also noted that, if you significantly increase your intake of dairy products while also increasing your overall calorie intake, it's likely that you would gain weight, although this weight would probably be in the form of fat and not lean muscle mass. On its own, an 8-ounce glass of full-fat milk contains 149 calories.
On the other hand, the report in the International Journal of Exercise Science notes that simply adding more calories in the form of milk protein probably won't contribute to weight gain on its own. Researchers from this study emphasize the importance of an exercise and resistance training regimen and say that, without one, your body composition probably won't change much just by drinking milk before bed. And if it does, the weight gain could be in the form of unhealthy fat or adipose tissue.
Drinking Milk and Strength Training
Based on this research, you could infer that drinking milk before bed could help you gain weight in the form of lean muscle, but only when combined with a regular strength training routine and increased calorie intake.
Instead of drinking a glass of plain milk, you can make weight gain milkshakes that have a combination of high-calorie, high-fat healthy ingredients, like full-fat milk (which hasn't been shown to increase heart disease risk), avocado, almond butter and a handful of fruit, to increase your overall calorie intake.
In addition to increasing your calorie intake, resistance training can help ensure that you're putting on weight in the form of muscle and not fat. Resistance training, also called strength training or weight training, is the use of resistance (usually in the form of weights or body weight) to increase the strength and size of your skeletal muscles. Examples of resistance training include:
- Free weights (dumbbells or kettlebells)
- Medicine balls or weighted bags
- Weight machines
- Resistance bands
- Suspension equipment (like TRX bands)
- Body weight (squats, push-ups and pull-ups)
The Cleveland Clinic notes that it will probably take a month or two of resistance training before you'll see a significant amount of weight gain from increased lean muscle mass, but if you stick with a regular routine and incorporate drinking milk before bed at night, you may be able to see the results you're after.
Disadvantages of Nighttime Milk
There may be some disadvantages of drinking milk at night, though. In addition to the possibility of undesirable weight gain in the form of fat, drinking milk too close to bedtime can disrupt digestion. Milk is fairly high in carbohydrates, with one 8-ounce cup containing about 12 grams, all of which are mostly in the form of lactose, a rapidly-digesting natural sugar.
Harvard Health Publishing notes that, when you consume a lot of food too close to bedtime — especially carbohydrates — it can result in overheating and night sweats since your body temperature and metabolism increases as you work to digest the food.
Digestive troubles are also a possibility. If you lie down too quickly after eating or drinking one of your weight-gain milkshakes, it can make digestion harder and cause the food to travel in reverse through your digestive tract. This can cause gastroesophageal reflux, or GERD (characterized by uncomfortable symptoms like heartburn, persistent coughing and chest pain) that can wake you up and keep you up at night.
On the other hand, an empty, rumbling stomach can keep you up, too. So, if you make sure to drink your milk at least two to three hours before bed and you keep your portion small, it's possible that the milk can help you sleep. According to the National Sleep Foundation, milk contains tryptophan, which can increase melatonin and lead to deeper, more restful sleep.
- International Journal of Exercise Science: "Casein Protein Supplementation in Trained Men and Women: Morning Versus Evening"
- Nutrients: "Pre-Sleep Consumption of Casein and Whey Protein: Effects on Morning Metabolism and Resistance Exercise Performance in Active Women"
- International Journal of Obesity: "Effect of Dairy Consumption on Weight and Body Composition in Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Clinical Trials"
- European Journal of Nutrition: "The Relationship Between High-Fat Dairy Consumption and Obesity, Cardiovascular, and Metabolic Disease"
- Mayo Clinic: "Gastroesophageal Reflux Disease (GERD)"
- Harvard Health Publishing: "Do People Really Get Nightmares From Eating Late?"
- National Sleep Foundation: "Food and Drink That Promote a Good Night's Sleep"
- Harvard Health Publishing: "8 Secrets to a Good Night's Sleep"
- Nutrition and Metabolism: "Milk Protein for Improved Metabolic Health: A Review of the Evidence"
- Cleveland Clinic: "I Just Started Exercising — Why Am I Gaining Weight?"
- Better Health Channel: "Resistance Training – Health Benefits"
- USDA National Nutrient Database for Standard Reference: "Milk, Whole, 3.25% Milkfat, With Added Vitamin D"