Does protein powder help you lose weight?
Only if it helps you eat fewer calories. A scoop adds calories like any food. Trials found extra protein added about 1 kg or less to weight loss. Two label numbers matter: calories and protein.
On this page
Do protein shakes help you lose weight?
Only as part of eating fewer calories. NICE says any weight-loss diet has to keep what you eat below what your body uses. A shake doesn’t change that rule.
More protein helps a little on top. In 24 trials, people on the same calorie-cut diet lost 0.79 kg more on a higher-protein diet. They also kept a little more lean tissue, such as muscle.
The authors called the benefit modest.
Source: Food labelling law (1169/2011)
Drink the same shake on top of your usual snack and your day goes up 150 kcal instead.
So pick one snack a shake could replace, not join.
Do you need extra protein to lose weight?
Most people don’t. The UK guide for adults is 0.75 g of protein per kg of body weight a day. That’s 56 g for a 75 kg man and 45 g for a 60 kg woman.
On average, UK men already eat about 85 g and women about 67 g. So the British Nutrition Foundation says most of us don’t need protein supplements.
- Below 0.8 g per kgBelow the UK guide for adults.
- 0.8 to just under 1.2 g per kgMeets the UK guide.
- 1.2 up to 1.6 g per kgRange one review suggests may help weight loss.
- Above 1.6 g per kgAbove that review’s range.
The 1.2 to 1.6 g range comes from one research review, not the NHS. For a 75 kg person that’s 90 to 120 g a day.
Busy and training hard? The foundation says a shake may be a handy way to get enough, though food is better where you can.
Try food first with high-protein breakfasts. Over 40? See protein after 40.
What is the best protein powder for weight loss?
The one with the most protein for its calories. Check the calories per serving, made up the way you’ll drink it, and the grams of protein.
Labels count protein at 4 kcal per gram. Times the grams by 4 to see how many calories come from protein.
Sources: Nutrition claims law (1924/2006); Food labelling law (1169/2011)
A “high protein” tub only needs 20% of its calories from protein. So for weight loss, pick a shake like A.
| On the tub | What the law allows |
|---|---|
| High protein | At least 20% of calories from protein |
| Low calorie (low energy) | 40 kcal or less per 100 g, or 20 kcal or less per 100 ml for drinks |
| Low sugar | 5 g of sugars or less per 100 g, or 2.5 g or less per 100 ml for drinks |
| Sugar-free | 0.5 g of sugars or less per 100 g or 100 ml |
| Low carb, keto or lean | No set meaning in the UK list of nutrition claims |
Source: Nutrition claims law (1924/2006)
Protein alone has 4 kcal a gram, so 100 g of powder can’t get near 40 kcal. Compare kcal per serving instead.
For keto or low carb, read the carbs line yourself.
Worried about the sweeteners in sugar-free tubs? The NHS says approved sweeteners are a safe alternative to sugar.
Five checks before you buy a protein powder
- Find the calories per serving, and add what you mix it with.
- Times the protein by 4 and compare it with the calories. More protein per calorie is better for weight loss.
- Check the sugars. Sugar-free means 0.5 g or less per 100 g or 100 ml.
- Ignore “lean” and “keto”. Read the carbs and calories lines instead.
- Check the bold allergens. Whey is made from cows’ milk.
Sources: Nutrition claims law (1924/2006); Food labelling law (1169/2011); NHS: food allergy
The same sums work for bars. See how to pick a healthy protein bar.
Whey or plant, and is it different for women?
Whey has been tested in weight-loss trials. In 9 trials in people with overweight or obesity, whey groups lost 0.56 kg more than groups given a dummy powder or no whey. They also lost 1.12 kg more fat.
We found no trials comparing whey with plant powders for weight loss. Can’t have dairy? See dairy-free protein powders.
We found no evidence for a special women’s formula.
In trials during a calorie cut in adults aged 18 to 50, more dairy food or whey led to 1.16 kg more weight loss. Those studies were mostly of women. The extra loss wasn’t seen in studies that added strength training.
Women aged 55 and over were different. Whey made no clear difference to weight or fat, with or without strength training. With strength training, whey helped leg muscle and arm strength in those trials.
Losing weight and want to keep your strength? See how to protect muscle during weight loss.
Protein shake or meal replacement shake?
They aren’t the same. A protein shake is mostly protein. A meal replacement has to meet set rules to claim it helps weight loss.
Each serving must have 200 to 250 kcal, with 25% to 50% of it from protein. To get that effect, the law says to replace two main meals a day in a calorie-cut diet.
In 23 trials of 7,884 adults with overweight or obesity, diets with meal replacements lost 1.44 kg more at 1 year than other diets.
Don’t swap your main meals for a 110 kcal protein shake. It isn’t a meal replacement. NICE warns that unbalanced, restrictive diets don’t work long term and can be harmful.
Thinking of a shake diet of 800 to 1,200 kcal a day? NICE says to consider one only for people living with obesity, or with overweight and type 2 diabetes. Even then, only with long-term support from a specialist service.
For other routes, see the best diet to lose weight.
When to speak to a GP
Protein powder is a food, but some people should check first. Speak to a GP or your care team if:
- You have kidney disease. Ask your kidney team first, as a kidney dietitian explains the risks of too much protein.
- You keep losing weight without changing your diet or exercise. The NHS says to see a GP, and as soon as possible if you have other symptoms too.
- You think you may have a food allergy. Common ones include cows’ milk, eggs, soybeans and peas.
- You want to try a shake diet of 1,200 kcal a day or less. NICE says these should be nutritionally complete, last no more than 12 weeks and include ongoing clinical support.
Call 999 if your lips, mouth, throat or tongue suddenly swell. Also call if you’re breathing very fast or struggling to breathe (you may be very wheezy or feel like you’re choking). The NHS lists these as signs of a serious allergic reaction.
Also call 999 if your throat feels tight or you’re struggling to swallow. The same goes if your skin, tongue or lips turn blue, grey or pale. On black or brown skin, this may be easier to see on the palms or soles of the feet.
Call 999 if you suddenly become very confused, drowsy or dizzy, or someone faints and cannot be woken up. The same goes if a child is limp, floppy or not responding like they normally do.
Wondering if a shake shows up in your bloods? See does whey protein affect a blood test.