Do Weight Loss Shakes and Meal Replacements Work?

Weight loss shakes can help some adults lose weight, because a shake that replaces a higher-kilojoule meal lowers the energy they take in. They are a short-term tool rather than a long-term plan: weight returns after the shakes stop if eating and exercise habits have not changed.

Everything here is general information, not medical advice. Outcomes vary between individuals, and a GP or accredited practising dietitian can tailor a plan to your health.

On this page

1. Key Points
2. What Are Weight Loss Shakes?
3. Meal Replacements vs Very Low Energy Diets
4. How Much Energy Do Shake-Based Diets Provide?
5. Using a Meal Replacement Shake
6. Do Weight Loss Shakes Work?
7. Side Effects and Downsides
8. Who Should Get Advice First
9. Protein Shakes vs Meal Replacements
10. Healthy Diet and Physical Activity Come First
11. Shakes Compared With Medical Weight Loss Treatment
12. Frequently Asked Questions

Key Points

• Shakes help with weight by lowering your total energy intake.

• Formulated meal replacements can replace some meals, not all. Very low energy diet (VLED) products replace every meal, under medical supervision.

• In one review, low energy diets using meal replacements led to more weight loss than food-based low energy diets, but shakes are not suited to long-term use.

• Protein shakes are a different product, and most Australians already get enough protein from food.

• A healthy diet and regular physical activity are still needed, during and after any shakes.

What Are Weight Loss Shakes?

A weight loss shake is a premixed drink, or a powder mixed with water or milk, that you have instead of a meal. Most are protein-based, made from milk or soy, with few carbohydrates and added vitamins and minerals. Shakes for weight loss are low in kilojoules, so swapping one for a larger meal helps create an energy gap: you take in less energy than your body uses.

Meal Replacements vs Very Low Energy Diets

Two kinds of shake look alike on the shelf. Food Standards Australia New Zealand (FSANZ) sets different rules for a formulated meal replacement (FMR) and a very low energy diet (VLED) product.

The VLED figures assume three serves a day. A VLED label must also say the product is not recommended for pregnant or breastfeeding women, infants, children, adolescents or older people other than under medical supervision, and that drinking enough fluid each day is important. Some other products advertised for weight loss are medicines, and these carry an AUST L or AUST R number on the label.

How Much Energy Do Shake-Based Diets Provide?

The Australian Obesity Management Algorithm, a primary care guide, describes three levels. A reduced energy diet uses everyday foods to cut 2,000 to 4,000 kJ a day. A low energy diet brings the daily total to 4,200 to 5,000 kJ (1,000 to 1,200 calories), and one or two meals can be meal replacements. A very low energy diet brings it under 3,300 kJ (800 calories) by replacing meals with meal replacement products.

Figures from healthdirect, the Better Health Channel and the primary care guide above. Individual needs vary.

For comparison, the average adult needs about 8,700 kJ a day. The Better Health Channel says a reputable weight management service advises against eating less than 5,000 kJ a day. Low and very low energy diets sit at or below that level, and a VLED needs regular clinical review, at least monthly.

Using a Meal Replacement Shake

• Replace some meals, not all. A formulated meal replacement can stand in for one or two meals a day, but it should not replace every meal.

• Eat well around it. Build your other meals from the five food groups: vegetables and legumes, fruit, grain foods, lean meats and alternatives, and milk, yoghurt, cheese or alternatives.

• Get advice first. Anyone using meal replacements for weight loss should do so with the help of a health professional.

Do Weight Loss Shakes Work?

They can support weight loss, with limits. A systematic review found that low energy diets using meal replacements led to more weight loss than food-based low energy diets. Only 12 of the studies replaced meals with shakes alone, and most or all participants in 18 of the 22 study groups were women. Healthy Male, a men's health organisation funded by the Australian Government, concludes that meal replacement shakes are not suitable for long-term use, and the evidence on whether they work is not settled.

In recent primary care studies, people on an 8 to 20 week VLED lost about 10 to 14.5% of their starting body weight on average. Outcomes vary between individuals.

Side Effects and Downsides

Common side effects of replacing every meal with very low energy diet products are constipation, feeling the cold more, headache and dizziness. The RACGP's handbook says these are usually mild to moderate and ease over time. Australian primary care guidance adds a teaspoon of olive oil to a VLED to reduce the risk of gallstones.

Shakes in general have other downsides:

• Nutrient gaps. A restricted diet can fall short on fibre, folate, B vitamins, iodine, iron and zinc. Adults need about 25 g (women) to 30 g (men) of fibre a day.

• Weight regain. Weight returns after the shakes stop if eating and exercise habits have not changed.

• Social life. Restricted eating can affect your social life, relationships and emotional health.

• Processing. Under the NOVA system, meal replacement shakes and powders count as ultra-processed foods.

• Cost. Very low energy diet brands sold through resellers can cost much more than pharmacy brands.

Who Should Get Advice First

Speak with your GP before starting any weight loss program, especially if you take medicines from your doctor or live with diabetes, high blood pressure, kidney, liver, heart or thyroid conditions, gallstones, gout, or a current or past eating disorder.

Australian clinical guides list extra reasons not to use a VLED, or to use it only with close care:

• pregnancy or breastfeeding

• a severe mental health condition, or alcohol or drug dependence

• a recent heart attack, stroke or unstable angina

• porphyria

• age over 65, because data for this age group are limited

• some diabetes medicines, kidney disease or blood-thinning medicine, where doses or monitoring may need to change

If you are considering a VLED, a dietitian can check that you still meet your nutritional needs, have ongoing support, and know how to return to regular meals. Be wary of programs that promise easy weight loss without a dietitian or doctor, rely on expensive supplements or shakes, or replace food with powders.

Protein Shakes vs Meal Replacements

A protein shake is not the same as a formulated meal replacement, which must meet the FSANZ rules for energy, protein, vitamins and minerals. The Better Health Channel says protein shakes, powders and supplements are unnecessary for most Australians, because 99% get enough protein from the food they eat. Protein the body does not need is either passed out as waste or stored as weight gain.

A higher-protein diet can help you feel fuller for longer, as part of balanced meals from all the food groups, and it is important not to take too much protein. Speak with your GP or a dietitian before adding protein supplements, and see how to calculate macros and protein for weight loss to check your own needs.

Healthy Diet and Physical Activity Come First

When you take in less energy than your body uses, the body draws on stored energy, mostly fat. A healthy diet built on the five food groups creates that gap without shakes. Anyone using shakes should also get guidance on their overall nutrition, aiming to meet the Australian dietary guidelines and the recommended amount of exercise each week.

Australia's physical activity guidelines for adults recommend moderate to vigorous activity for 30 minutes or more on most days, plus muscle-strengthening activities on 2 or more days a week.

For the wider plan, read how to lose weight, what a calorie deficit is and how to work out yours, how many calories a day you need to lose weight and how many steps a day can support weight loss.

Shakes Compared With Medical Weight Loss Treatment

For adults with obesity who have not lost enough weight on a reduced or low energy diet, Australian primary care guidance lists two options: a very low energy diet, or adding weight loss medication.

Weight loss medication is used while reducing kilojoule intake and increasing physical activity, not instead of them. It has side effects and can be harmful for some people, so any medical treatment is a decision for a doctor or nurse practitioner after an individual assessment. Outcomes vary between individuals. To learn more, read how medical weight loss programs work, or, if you live with type 2 diabetes, weight loss medication and type 2 diabetes.

Where shakes have come and gone without a change that holds, Burst Health provides medical weight loss plans online, each reviewed by an Australian-registered doctor or nurse practitioner before it starts: check whether you are eligible.

Frequently Asked Questions

Is there a weight loss shake that actually works?

No single shake causes weight loss. Australia's food regulator lets meal replacement labels link weight loss only to their energy content, not to the food itself, citing concern that no one food has weight-reducing properties of its own. A shake can help when it replaces a meal with more kilojoules, so your total energy intake falls. Outcomes vary between individuals.

Can you lose weight just drinking meal replacement shakes?

It is possible only with very low energy diet products, which are made to replace every meal for up to 12 weeks under the supervision of a doctor and dietitian. Ordinary meal replacement shakes are not made for that: their labels must say they are not for use as a total diet replacement. Living on shakes without that support risks nutrient gaps and weight regain.

Will I lose weight on 2 shakes and 1 meal a day?

It depends on the total energy in your day. Australian GP guidance describes a supervised plan of two meal replacements, usually at breakfast and lunch, plus lean protein and vegetables at dinner. If the day's total is under 3,300 kJ, the plan is a very low energy diet, which needs clinical review at least monthly. Outcomes vary between individuals, so talk to your GP or a dietitian first.

Are protein shakes good for weight loss?

No, most people do not need them. Most Australians already get enough protein from the food they eat. A protein shake is also not the same as a formulated meal replacement. If you want more protein, check with your GP or a dietitian first.

What is the best shake for weight loss?

There is no single best shake for everyone. Check that the label says "Formulated Meal Replacement" or "Very Low Energy Diet", compare protein, energy and fibre per serve, and plan the rest of your meals around healthy foods. A GP or accredited practising dietitian can help you choose whether a shake suits your health and goals.

References

• Food Standards Australia New Zealand. Very Low Energy Diets vs Formulated Meal Replacements: information for consumers.

• Food Standards Australia New Zealand. Very Low Energy Diets vs Formulated Meal Replacements: information for health professionals.

• Food Standards Australia New Zealand. Very low energy diets (VLED).

• Food Standards Australia New Zealand. EU claims: meal replacements and body weight.

• Markovic TP, et al. The Australian Obesity Management Algorithm: a simple tool to guide the management of obesity in primary care (July 2024).

• Royal Australian College of General Practitioners. Handbook of Non-Drug Interventions (HANDI): VLED for type 2 diabetes.

• Healthy Male. Male weight loss shakes: do they work and are they good for you?

• Better Health Channel (Victorian Government). Weight management services.

• Better Health Channel (Victorian Government). Protein.

• Better Health Channel (Victorian Government). Dietary fibre.

• healthdirect. Kilojoules.

• healthdirect. Protein.

• healthdirect. Weight loss and dieting.

• healthdirect. Ultra-processed foods: what are they and which ones should I avoid?

• healthdirect. Obesity.

• Eat for Health (NHMRC). Australian dietary guidelines 1 - 5.

• Australian Government Department of Health. Physical activity and exercise guidelines for adults (18 to 64 years).

This article is general information only and does not replace individual medical advice. Please speak with a registered Australian healthcare practitioner about your own circumstances.