How Many Meals a Day Should You Replace with a Shake to Lose Weight?

Written by Andrew Hill, Level 4 Personal Trainer and fat loss coach. Last updated 8 November 2026.

It’s the question I’m asked more than any other: “How many shakes should I have a day?” The answer depends on whether you’re trying to lose weight or keep it off, and there’s clear, UK-approved guidance on both. This guide is part of our complete UK guide to meal prep for weight loss.

What the approved UK guidance says

In Great Britain, health claims on food have to be authorised and appear on the government’s nutrition and health claims register^[1]. For meal replacements for weight control that meet the required nutritional standard, two claims are permitted:

• “Substituting two daily meals of an energy-restricted diet with meal replacements contributes to weight loss.”
• “Substituting one daily meal of an energy-restricted diet with a meal replacement contributes to the maintenance of weight after weight loss.”

Two conditions go with these claims: the meal replacement is only useful as part of an energy-restricted diet, and other foods should be part of that diet. It’s also important to drink enough fluids each day.

Herbalife Formula 1, made as directed, is designed as a meal replacement for weight control.

What the research shows

Meal replacements are one of the better-researched tools in weight management. A 2019 systematic review and meta-analysis of randomised trials found that programmes including meal replacements led to greater weight loss at one year than diet programmes without them^[2]. An earlier pooled analysis of six studies reached a similar conclusion for partial meal replacement plans^[3].

Why do they help? Mostly because they take the guesswork out of portion sizes and calorie counting for one or two meals a day, which makes a reduced-calorie diet easier to stick to.

One shake or two: how to choose

Many people start with one shake a day to build the habit, then move to two. That’s a perfectly sensible approach.

What should your other meal look like?

This is where most shake plans go wrong. The evening meal needs to be a proper, balanced meal:

• Half a plate of vegetables or salad.
• A palm-sized portion of protein: chicken, fish, eggs, tofu, beans or lentils.
• A sensible portion of high-fibre carbohydrate, such as brown rice, wholemeal pasta or potatoes with skins.

The NHS Eatwell Guide shows the balance to aim for across the day^[4]. Add healthy snacks such as fruit, yoghurt or a protein bar if you’re hungry, and drink plenty of water.

Is replacing every meal a good idea?

Not without medical support. Replacing all meals with formula products, known as total diet replacement, can produce very low calorie intakes. Very low calorie diets, below 800 calories a day, are only suitable for some people, for a limited time and under medical supervision^[5]. The DiRECT trial, which used total diet replacement for people with type 2 diabetes, was delivered through GP practices with clinical support^[6]. That’s very different from a home routine.

Who should speak to their GP first?

Check with your GP or pharmacist before using meal replacements if you:

• have diabetes, especially if you take insulin or tablets that can cause low blood sugar;
• take regular medication, or have a heart, kidney or liver condition;
• are pregnant or breastfeeding;
• have, or have had, an eating disorder;
• are under 18.

Andrew’s tip

Start with breakfast. It’s the meal most people skip or grab on the go, and replacing it with a shake gives you an easy win from day one. Once that feels automatic, decide whether a lunchtime shake suits your week too.

Frequently asked questions

Can I have three shakes a day?

We don’t recommend replacing every meal without medical supervision. Two shakes plus a balanced meal and healthy snacks is the approved approach for weight loss.

How long can I use meal replacement shakes?

Many people use one shake a day long term as part of a balanced diet, which is the approved approach for maintaining weight after weight loss^[1].

How does Formula 1 compare with other shakes?

See our Formula 1 vs other meal replacement shakes comparison.

Next, read how to stay full on a calorie deficit or what is the Herbalife diet?

This guide is general information, not medical advice. If you have a medical condition, are pregnant or breastfeeding, take regular medication or are under 18, speak to your GP before changing your diet. DietPal is run by Andrew Hill, an Independent Herbalife Member who earns money when you buy Herbalife products from DietPal. How I earn money.

References

1. Department of Health and Social Care. Great Britain nutrition and health claims (NHC) register. gov.uk
2. Astbury NM, et al. (2019). A systematic review and meta-analysis of the effectiveness of meal replacements for weight loss. Obesity Reviews. doi:10.1111/obr.12816
3. Heymsfield SB, et al. (2003). Weight management using a meal replacement strategy: meta and pooling analysis from six studies. International Journal of Obesity. doi:10.1038/sj.ijo.0802258
4. NHS. The Eatwell Guide. nhs.uk
5. NHS. Very low calorie diets. nhs.uk
6. Lean MEJ, et al. (2018). Primary care-led weight management for remission of type 2 diabetes (DiRECT): an open-label, cluster-randomised trial. The Lancet. doi:10.1016/S0140-6736(17)33102-1