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Written by: Alex Bussey
Edited by: Meera Senthilingam
Reviewed by the Your.MD medical team
Fitness supplements have been popular for some time, with people often taking them in hope of building muscle or losing weight.
You might see them on the shelves of your local supermarket, the fitness section of a pharmacy or a health shop. But do they actually work?
Evidence suggests that they may help with some types of exercise, but experts warn that they’re not always a good substitute for a balanced diet. They can also have serious side effects.
Here’s everything you need to know about fitness supplements.
There are 2 main types of fitness supplement and they're used for either protein boosts or weight loss.
These are normally powders, bars, shakes or gels that are supposed to provide your body with large amounts of protein.
Some people believe that protein supplements make it easier to build muscle, increase your strength, control your appetite or boost your energy levels.
These are supposed to help you lose weight by stopping your body from absorbing fat, or by speeding up your metabolism so that you can lose weight more quickly.
Some weight loss supplements also claim to suppress your appetite or make you feel full for longer to help you to lose weight without changing your diet.
But there isn’t much evidence to support these claims and some fitness supplements could be dangerous.
It’s hard to say whether fitness supplements are helpful. Some athletes could benefit from a regular protein supplement — particularly if they’re doing a lot of resistance training, or struggling to get enough protein from their diet.
But experts say most people should focus on eating a balanced and healthy diet instead.
There’s also little or no evidence to support the use of weight loss supplements.
Protein supplements provide large amounts of protein — an essential nutrient that’s used to build new muscle and repair some of the muscle tissue that’s normally damaged during exercise.
But most people get more than enough protein from their diet.
The British Nutrition Foundation says that you should aim to eat about 0.75g of protein per kilogram of bodyweight every day. That’s about 56g of protein for the average man and 45g of protein for the average woman.
And most people eat about 68g of protein a day, with any extra protein then burned to provide energy. So there’s usually no need to take a protein supplement unless a doctor or dietitian has advised you to, for example if you’re a professional athlete.
Athletes burn more energy than the average person. They also do more damage to their muscles, and eating more protein helps to repair some of this damage.
Groups like the International Society of Sports Nutrition (ISSN) say that professional athletes should aim to eat about 1.4 to 2.0 grams of protein per kg of body weight — more than double the normal recommendation.
Taking a high-quality protein supplement can help with this — particularly if you don’t have time for a meal or a snack.
But some experts warn that protein supplements aren’t always a healthy choice. They often lack the vitamins and minerals that are found in more complex food and groups like the British Dietetic Association say that it may be better to focus on eating foods that are naturally high in protein.
Weight loss supplements often contain ingredients like caffeine, raspberry ketones (a natural chemical found in red raspberries) or green tea. These ingredients are supposed to stop your body from absorbing fats, reduce your appetite or speed up your metabolism.
But there isn’t much evidence to support these ideas. This is partly because the companies that make weight loss supplements don’t always carry out studies on people to make sure that their products work.
The US-based Office of Dietary Supplements (ODS) also notes that when studies are carried out, they're often too small or poorly-designed to tell us anything useful.
If you’re trying to lose weight, it’s best to focus on methods that are proven to work. This includes things like getting plenty of exercise or making long-term changes to your diet.
You could also try talking to a doctor if you’re struggling to lose weight. They may be able to give you some additional support.
Protein supplements can be bought without a prescription, but that doesn't mean that they’re safe to take.
These supplements aren't tested as rigorously as other medications and research shows that up to 5% of fitness supplements could contain anabolic steroids and other unlabelled ingredients. Steroids can lead to many physical problems, including high blood pressure, liver damage, stroke or heart attack. They can also cause mania and delusions.
Some weight loss supplements also contain illegal or dangerous ingredients — including things like 2,4-Dinitrophenol (DNP). This ingredient is an industrial chemical that speeds up your metabolism. It’s highly toxic and has been linked to at least 3 deaths. DNP has been banned as a weight loss drug in the USA, and in the UK it has been labelled a hazardous chemical.
Weight loss supplements can also interfere with other drugs and may have serious side effects. Before you take any supplements, you should always check with your doctor to make sure it's safe for you to do so.
Experts further warn that eating too much protein could increase your risk of osteoporosis and make some kidney problems worse. To avoid these side effects, avoid eating more than twice the recommended amount of protein.
But always talk to a doctor before you start taking a protein supplement.
Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.