HYPE: Replacing meals with formulated shakes produces better weight-loss results than ordinary food.
But what does the evidence actually show?
Structured programmes using meal replacements often produce greater average weight loss than the comparison diets tested, including at one year.
This is meaningful clinical evidence. It supports a programme option, not an inherent fat-loss property of liquids. Products, calorie targets, behavioural support and the transition back to ordinary meals all matter.
The claim — three products that should not be confused
A partial meal-replacement programme replaces some meals while keeping others. A total diet-replacement programme initially uses a formulated diet in place of ordinary meals, followed by food reintroduction. A protein supplement mainly adds protein and is not automatically designed to supply a complete meal or an entire day’s nutrition.
Even among products sold as meal replacements, intended use and nutritional composition differ. A branded powder should not inherit the results of a supervised programme simply because both are mixed in a shaker.
What the evidence shows
Astbury and colleagues (2019)
A review of 23 randomised trials involving 7,884 adults found greater one-year weight loss with programmes incorporating meal replacements. In comparisons with support provided to both groups, the average advantage was about 2.2 kg, with substantial variation between studies. The review excluded total diet replacement and diets below 800 kilocalories per day. [1]
Read the researchThat is evidence for a real, usually modest average advantage in partial-replacement programmes. It also shows why support cannot be ignored: comparisons that change both the diet and the amount of help answer a broader question than “shake versus food”. Only six of the 23 trials were assessed as low risk of bias across all domains, so confidence should remain proportionate.
Total diet replacement can produce larger losses
DROPLET (2018)
In 278 adults with obesity, an initial formula diet providing 810 kilocalories per day, followed by food reintroduction and behavioural support, produced greater one-year weight loss than usual nurse-led care. Average losses were 10.7 kg versus 3.1 kg; the adjusted difference was 7.2 kg. Follow-up was incomplete, and this was a whole treatment programme rather than an equal-calorie comparison of liquids and solids. [2]
Read the researchThe low-energy phase was time-limited. Reproducing only the shake purchase would not reproduce the intervention. Its structure can make portions and daily decisions simpler, but the trial does not separate those benefits from the prescribed energy intake and ongoing support.
What happens after the initial loss?
At three years, the DROPLET follow-up still favoured total diet replacement: the adjusted difference was 3.3 kg. However, substantial regain occurred after the programme ended, and outcome measurements were available for 66% of participants. The remaining advantage is useful; it is not evidence that maintenance becomes effortless. [3]
This also avoids a misleading either-or story. Greater regain after a larger initial loss does not erase every benefit, and a lower average weight at follow-up does not mean nobody struggled. A maintenance plan is part of the treatment question, not an optional afterthought.
Why “better than food” overstates the evidence
These trials generally compare usable weight-management strategies. They do not hold every calorie, nutrient, contact session and adherence pattern identical while changing only texture. It is therefore more accurate to say that structured meal-replacement programmes can outperform the tested alternatives.
For some people, predictable portions and fewer decisions are useful. Others prefer the variety, chewing and social flexibility of conventional meals. The clinical results do not establish universal superiority for hunger control or satisfaction. Cost, taste and the ability to maintain the routine affect the practical choice.
The catch
- Different interventions have different results. A partial replacement at lunch is not the same treatment as a total diet-replacement programme.
- Commercial involvement deserves transparency. The review authors disclosed weight-management industry research relationships, and DROPLET received a Cambridge Weight Plan research grant. These links do not negate the findings, but strengthen the case for independent replication.
- Follow-up and bias matter. Missing participants and varied support make the exact size of the advantage uncertain.
- Nutrition and safety are product- and person-specific. A restrictive plan should not be improvised from ordinary protein shakes.
What this means for you
A well-designed partial meal replacement can be a legitimate convenience tool. Check what the product is intended to replace and how the rest of the diet supplies adequate nutrition. Adding a shake on top of unchanged meals is a different intervention from replacing one.
NICE places low-energy and very-low-energy diets within supported, multicomponent care. Such diets should be nutritionally complete, last no more than 12 weeks, and include clinical supervision and food-reintroduction advice. Medication and eating-disorder considerations should be reviewed before starting. [4]
If considering a restrictive total replacement programme, discuss suitability with an appropriately qualified clinician or dietitian. Decide in advance how ordinary meals and longer-term support will return. The trial calorie levels describe research, not a self-prescription.
The structured programme has evidence. The liquid format is not magic.
Meal replacements are one valid weight-management option; conventional foods remain compatible with an effective, sustainable plan.
Research & Sources
1. Astbury et al. (2019)
Meal replacements for weight loss: systematic review and meta-analysis.
Read the source2. Astbury et al. (2018)
DROPLET: total diet replacement versus usual care, randomised trial.
Read the source4. NICE, NG246
Overweight and obesity management: physical activity and diet recommendations.
Read the sourceEvidence reviewed: October 2026
Evidence vs Hype explains scientific research for educational purposes and does not provide individual medical diagnosis or treatment.
For another dietary approach, see volume eating and the evidence on energy density. The question there is food composition and portion size, rather than a liquid meal-replacement format.