Meal replacement shakes: when they work

By the DieticiansWorldwide.com editorial team · 17 October 2026 · Weight management & GLP-1

What counts as a meal replacement

"Meal replacement" covers three quite different things, and confusing them is behind much of the mixed advice online.

• Partial meal replacement means swapping one or two meals a day for a nutritionally formulated shake, soup or bar, and eating ordinary food for the rest.
• Total diet replacement (TDR) means replacing all food for a set period with formula products, usually as part of a clinical programme, followed by a planned return to food.
• Protein shakes and smoothies are often sold alongside meal replacements but are not designed to replace a meal. Many contain protein and little else; others are high in sugar and calories.

The distinction matters in law, too. In the European Union, the authorised health claim for meal replacements applies only to foods that meet set compositional rules, with 200 to 400 kcal per meal and protein providing 25% to 50% of energy (Directive 96/8/EC). Total diet replacement products have their own regulation, applying since 27 October 2022, which requires 600 to 1,200 kcal and 75 to 105 g of protein for the whole day (Commission Delegated Regulation (EU) 2017/1798). The same regulation bans nutrition and health claims on TDR products, apart from "added fibre" when the product contains at least 10 g.

A shake sold as a "meal replacement" outside those rules, or in a country without them, may not meet any of these standards. Reading the label matters more than the name on the front.

Do meal replacement shakes work for weight loss?

Partial meal replacement

The most useful single source is a systematic review and meta-analysis of 23 randomised trials with 7,884 adults, which excluded very-low-energy diets and total diet replacement (Astbury and colleagues, Obesity Reviews 2019). At one year, diets incorporating meal replacements produced 1.44 kg more weight loss than alternative diets. The gap grew with support: 2.22 kg when both groups had support, 3.87 kg against diets without support, and 6.13 kg when meal replacements came with an enhanced level of support compared with regular support.

That pattern is the key finding. The shake is a tool; the support around it seems to do much of the work.

A more recent meta-analysis looked specifically at people with prediabetes or features of metabolic syndrome. Across 10 trials with 1,254 participants, meal replacements led to 1.38 kg more weight loss than conventional food-based weight-loss diets, with small improvements in LDL cholesterol and systolic blood pressure and a trivial change in HbA1c. The certainty of the evidence was rated low to moderate (Obesity Reviews 2024). If prediabetes is your reason for losing weight, our guide to the prediabetes diet sets out the food-based approach that shakes would be compared against.

Total diet replacement

Total diet replacement produces much larger losses, but it is a clinical treatment, not a supermarket diet.

• DROPLET. In this UK primary care trial, 278 adults with obesity were randomised to a programme using formula products providing 810 kcal a day as the sole food for eight weeks, followed by food reintroduction and behavioural support, or to usual care from a practice nurse. At 12 months, the TDR group had lost 10.7 kg against 3.1 kg, and 45% had lost 10% or more of their weight against 15% (Astbury and colleagues, BMJ 2018).
• DiRECT. In people with type 2 diabetes diagnosed within the past six years, a programme of withdrawing diabetes and blood pressure medicines, an 825 to 853 kcal formula diet for 3 to 5 months, stepped food reintroduction and long-term support led to remission in 46% of participants at 12 months, against 4% in the control group (Lean and colleagues, Lancet 2018). At 24 months, 36% of the intervention group remained in remission (Lean and colleagues, Lancet Diabetes & Endocrinology 2019).

In DiRECT, remission tracked weight loss closely: it was achieved by 86% of participants who lost 15 kg or more, 57% of those who lost 10 to 15 kg, and none of those who gained weight. Remission here means blood glucose below the diabetes threshold without medication; it is not a cure, and it can be lost if weight returns.

How many meal replacement shakes a day?

The EU's authorised health claims give the clearest answer for partial replacement. Substituting one daily meal of an energy-restricted diet with a meal replacement "contributes to the maintenance of weight after weight loss", and substituting two daily meals "contributes to weight loss" (Commission Regulation (EU) No 432/2012). Both claims apply only to products meeting the compositional rules above, and only as part of a diet that is restricted in energy overall.

In practice, that means:

• Two shakes a day for an active weight-loss phase, with one balanced meal built around vegetables, protein and whole grains.
• One shake a day for maintenance, if it helps you keep to your plan.
• Full replacement only within a supervised programme. NICE says low-energy diets of 800 to 1,200 kcal a day should be considered only as part of a multicomponent strategy with long-term support, and that very-low-energy diets under 800 kcal a day are for people with a clinically assessed need to lose weight rapidly, within a specialist service (NICE NG246).

If you are unsure what your daily energy needs are, the calorie calculator gives a starting estimate to plan shakes and meals around. Our separate article on the very-low-calorie diet explains the safety requirements for the most restrictive programmes.

How to choose a meal replacement shake

Because we do not recommend brands, use the label. These are the features worth checking.

Protein

Protein helps fullness and protects muscle during weight loss. A product meeting the EU meal replacement standard provides 25% to 50% of its energy from protein, which for a 200 to 400 kcal serving works out at roughly 12.5 g to 50 g. Products at the lower end of that range are less filling. If you also take a GLP-1 medicine, protein becomes more important still, as our guide to GLP-1 weight loss explains. For general protein products, see our review of protein powder.

Energy

A meal replacement should replace a meal, not add to one. Check the energy per serving as you will actually make it up. Mixing powder with whole milk instead of water, or blending in nut butter and banana, can turn a 200 kcal shake into a 500 kcal one.

Sugar

Look at "carbohydrates, of which sugars" per 100 g. The NHS describes more than 22.5 g of total sugars per 100 g as high and 5 g or less as low, and sets an adult limit of 30 g of free sugars daily (NHS). Some sugars in milk-based shakes come from lactose and are not free sugars, so read the ingredients list for added sugar, syrups and fruit juice concentrates.

Fibre

Fibre helps fullness and bowel regularity, which matters because NICE lists constipation among the risks of very-low-energy diets. Choose products that list a meaningful amount of fibre, and keep drinking water.

Vitamins and minerals

A product used as a meal replacement should be fortified to cover a meal's share of micronutrients. If you use two a day, the fortification matters more. Avoid stacking several fortified products and supplements without checking the totals.

Ingredients you may need to avoid

Check for allergens, caffeine, and stimulant or "fat-burning" additives, which have no place in a meal replacement. People with kidney disease should check protein, potassium and phosphate with their renal team.

Are meal replacement shakes healthy?

They can be part of a healthy plan, but they are not a healthy diet in themselves. Their strengths are structure, portion control and convenience: you know exactly what you have eaten, and they remove decisions at the meals people find hardest. Their weaknesses are that they do not teach cooking, shopping or eating out, and that many people find them monotonous.

NICE's obesity guideline is clear that diets which are both restrictive and nutritionally unbalanced fail over time and can do harm, and that the long-term aim is a balanced diet. A well-formulated meal replacement in a planned programme is different from a sugary shake used to skip meals, and the evidence above applies only to the former.

Why people regain weight after stopping, and how to avoid it

Regain is the most common problem with any intensive weight-loss method, and shakes are no exception. NICE advises professionals to explain before a low-energy diet starts "that weight regain is likely to happen, and if it does it is not because they or their healthcare professional have 'failed'". DiRECT shows the pattern: 46% were in remission at 12 months and 36% at 24 months.

The programmes with the best results build the transition into the plan:

1. Stepped food reintroduction. DiRECT used a 2 to 8-week phase, and DROPLET reintroduced food after eight weeks of TDR, rather than stopping abruptly.
2. Ongoing support. The meta-analysis results improved sharply with more support, and NICE requires long-term support for low-energy diets.
3. A maintenance shake, if it helps. The EU maintenance claim is based on replacing one meal a day.
4. Habits beyond the scale. Cooking skills, regular activity, sleep and planning for social events matter more once the shakes stop. Tracking non-scale victories such as energy, fitness and blood pressure helps keep motivation when weight plateaus.

Medication-first or lifestyle-first?

With GLP-1 medicines now widely used, people often ask whether shakes and diet programmes are still worth it. The two approaches answer different needs. Medicines produce larger average weight loss, but regain is common when they stop. Structured diet programmes using meal replacements produce smaller average losses, with large effects for some people, especially in early type 2 diabetes.

In practice, they are increasingly combined. Some people use shakes to meet protein needs when appetite is low on medication; others try a structured programme first and add medication if they need it. Our guides to medical weight loss and to comparing weight management programs set out the options side by side.

Weight-neutral care, stigma and outcome targets

A weight-loss target is not everyone's goal; weight-neutral practitioners track eating habits, fitness and blood results instead of kilograms. There is a real tension here. Trials of meal replacements are built around weight targets, and in type 2 diabetes the amount of weight lost strongly predicted remission. But a rigid focus on numbers can feel stigmatising, and for some people it can trigger disordered eating.

A good plan holds both: it is honest about what the evidence shows for weight, and it respects that you decide what you want to change. Before choosing an approach, the BMI calculator gives a standard starting figure that a professional can interpret alongside waist size, health conditions and your own goals.

Book a session with a dietitian

Who should not use meal replacements without medical supervision

• Pregnancy and breastfeeding. Weight-loss diets are not usually appropriate. Speak to your midwife or doctor.
• Eating disorders. NICE wants anyone starting a low-energy diet to be screened for eating disorders first. A rigid, formula-based plan can reinforce restriction or bingeing.
• Kidney disease. High-protein products may not be suitable; ask your renal team.
• Older adults. Weight loss in later life needs care to protect muscle and nutrition, as our guide to weight loss in elderly people explains.
• Children and teenagers. EU rules describe total diet replacement products as intended for adults with overweight or obesity, and weight-loss products should not be given to children without medical advice.
• Anyone taking several medicines should ask a pharmacist or doctor to review them before starting a low-energy plan, as NICE advises.

The practical takeaway

Meal replacement shakes are neither a gimmick nor a magic solution. Used to replace one or two meals within an energy-restricted diet, they add a modest amount of weight loss on average, and much more when combined with good support. Total diet replacement can produce large losses and, in early type 2 diabetes, remission, but it belongs in supervised programmes. Choose products by protein, energy, sugar and fibre, plan the return to food from the start, and treat maintenance as part of the treatment. For wider context, see our weight management guide.