Do weight loss supplements really work?

Australians spend more than a billion dollars¹ every year on weight loss supplements.

It’s not surprising, when the pills and powders promise quick and easy weight loss by reducing appetite, boosting metabolism, blocking the absorption of carbohydrates and burning fat.

If you’re feeling frustrated with plateauing progress through diet and exercise, a quick fix can sound enticing. But can these supplements really do what they claim? And do they have a place in a healthy weight loss plan? Let’s take a deeper dive.

Dietary supplements for weight loss include tablets and capsules, liquids, powders and snack bars.

Common ingredients include caffeine, green tea, guarana, African Mango, cola nut, raspberry ketone and capsaicin (a chilli pepper extract).

Common claims include:

• Reduced appetite: To make you less inclined to eat and/or promote a feeling of fullness, so you eat fewer calories, and are less tempted to snack between meals.
• Increased metabolism: To speed up your metabolism, which burns more fat. This is known as thermogenesis and is naturally achieved through exercise.
• Reduced absorption of fat or carbs: They claim to stop the body absorbing certain nutrients, particularly fat or carbohydrates.
• Hormone disruption: They claim to affect glucagon-like peptide 1 (GLP-1), a naturally occurring hormone that helps regulate blood sugar and appetite.
• Water removal: They claim to help you remove ‘water weight’.

While these mechanisms sound promising to anyone wanting to lose weight, there’s little scientific evidence² to support these claims.

“Weight loss supplements can support rapid weight loss, but they’re only usually recommended in the event of required pre-surgery weight loss, such as for bariatric surgeries, and is at the discretion of one's surgeon,” says GP and Bupa Clinical Lead Sam Saling.

“Many of these products are not evidence-based and are poorly regulated.”

The scientific consensus is that most over-the-counter supplements produce little to no meaningful long-term weight loss.

Some herbal supplements, like caffeine and green tea extract, may slightly boost how much energy your body uses. But the amount of weight loss they cause is so small that it isn’t considered meaningful for your health.³

Meal-replacement shakes or soups can be a helpful way to kick-start weight loss, especially if you follow a structured plan.

An Australian study found most people lost at least 5% of their body weight in 12 weeks, but keeping the weight off long-term usually means moving to a balanced, whole-food way of eating.⁴

“A better alternative to start with is to work with your GP to make lifestyle changes that assist with good health, and weight loss to follow,” says Dr Saling.

“Regular exercise, a healthy Mediterranean diet and adequate sleep are the foundation of any weight loss plan.”

The effectiveness of weight loss supplements is often unclear, and their safety isn’t always guaranteed.

Unlike prescription medicines, supplements aren’t strictly regulated.

Manufacturers don’t always have to prove their products are safe or effective before selling them.

Check the label:

• AUST R means the product is a registered medicine, like prescription or some over-the-counter drugs. These are reviewed by the Therapeutic Goods Administration (TGA) for safety, quality, and effectiveness.
• AUST L means it’s a listed medicine, like many vitamins and supplements. These are considered lower risk, but their effectiveness hasn’t been evaluated by the TGA.

Common side effects of some weight loss supplements include insomnia, rapid heartbeat, stomach upset, headaches, anxiety, and dehydration.

Unregulated products bought online may contain hidden or banned ingredients that could cause serious health problems such as liver damage.

Supplements can also interact poorly with other medications you are taking.

Always consult a GP or pharmacist before taking any supplement, and pay attention to any adverse effects. If you experience any of the above side effects, stop taking the supplement.

Sustainable weight loss comes from combining a balanced, whole-food, portion-aware diet with regular physical activity and behavioural change around optimising sleep and stress management.

If supplements are used, they should do just that, supplement, not replace, your existing healthy habits.

“If this is not enough, working with your doctor is the next step, as there are medications to support weight loss that are evidence-based and safe for many patients,” says Dr Saling.

Over-the-counter weight loss supplements are very different from prescription medications, which are clinically tested, regulated by the TGA, and taken under a doctor’s supervision for a specific medical reason.

Supplements are self-chosen, less strictly regulated, and often lack strong evidence.

Whatever approach you take, weight loss works best when combined with healthy eating and regular physical activity.

Find all the Australian dietary guidelines at The Australian Guide to Healthy Eating.

Bupa’s Dietitian Health Coaching provides guidance, information, and support across a wide range of nutrition areas at no extra cost for eligible Bupa members.