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This is a plain English summary of an original research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.

A programme of weekly behavioural support with total diet replacement led to over 7kg greater weight loss than usual care in primary care. This weight loss was maintained for a year after starting the 8-12 week low calorie programme.

This trial, funded by NIHR and a commercial sponsor, was carried out in ten primary care practices in Oxfordshire. Participants had BMI over 30. It referred half of the 278 participants to a commercial weight loss programme, free of charge for six months. The rest of the participants received usual care from their practice for 12 weeks.

Participants initially replaced all food with four formula food products daily (soups, shakes, and bars) containing 810 kcal per day. After eight weeks of this low calorie diet, conventional meals were gradually reintroduced.

This trial provides evidence that the rapid weight loss from these replacement diets can be maintained for a reasonable time and so could be considered as a treatment option for anyone who is obese and needs support to lose weight.

Why was this study needed?

In 2016, 26% of adults in England were obese. Obesity can lead to several medical conditions, including heart disease, type 2 diabetes and some cancers. Losing weight reduces the health risks for individuals. Treatments include increasing physical activity, reducing calorie intake, weight-loss drugs, and weight-loss (bariatric) surgery.

There is already some evidence that very low energy diets (fewer than 800 calories a day) can help people to lose weight, and keep more weight off after a year. However, all these trials took place in specialist clinics or research centres. None was carried out in routine primary care.

The NHS does not routinely offer these very low energy diet programmes. This study looked at referral by GPs to a commercially-provided low energy diet delivered by replacing food-based meals, compared with usual support in primary care.

What did this study do?

The DROPLET randomised controlled trial recruited 278 obese adults (BMI over 30) who wanted to lose weight. Half (138) were assigned to the diet replacement programme, and 140 were given usual care and support in primary care.

Those referred to their local Cambridge Weight Plan UK counsellor met weekly for three months. For eight weeks participants consumed 810kcal per day from meal replacement products, 750ml of skimmed milk, 2.25 litres of water or other low or no energy drinks, and a fibre supplement. This was followed by a four-week reintroduction of usual meals. There was then a 12-week maintenance phase, with monthly support appointments.

The usual care group had a 12-week programme of support from practice nurses and received a booklet about losing weight.

This was a pragmatic trial which couldn’t control every aspect of care. Participants and clinicians were aware of which treatment they were receiving, but this type of trial reflects the real world better. No-one in the usual care group could be referred to the programme once enrolled.

What did it find?

  • People in the diet replacement group lost more weight by 12 months than the usual care group. The mean weight change was -10.7kg (standard deviation [SD] 9.6kg) in the diet replacement group, and -3.1kg (SD 7.0kg) in the usual care group. The adjusted difference in mean weight change between the diet replacement and usual care groups was -7.2kg (95% confidence interval [CI] -9.4 to -4.9kg).
  • More people in the diet replacement group had lost 5% of their baseline body weight at 12 months: 73% in the diet replacement group vs 32% in the usual care group (adjusted odds ratio [OR] 6.5, 95% CI 3.4 to 12.2). Similarly, 45% of the diet replacement group had lost 10% of their baseline body weight, compared to 15% of the usual care group (adjusted OR 4.9, 95% CI 2.4 to 9.9).
  • After 12 months, the diet replacement group had greater reductions in HbA1c, (adjusted difference ‑2.2mmol/mol, 95% CI -4.4 to 0.0mmol/mol). HbA1c is a measure of a person’s average blood glucose levels for the previous two to three months. Higher levels indicate type 2 diabetes.
  • Mild adverse events were common in both groups: 51% of people in the diet replacement group and 30% in the usual care group experienced at least one side effect. The most common of these in the diet replacement group were constipation, fatigue, headache and dizziness.

What does current guidance say on this issue?

NICE updated its guideline on the identification, assessment and management of obesity in 2014. It says that very low calorie diets of 800 kcal per day or less should not be routinely used to manage obesity. These very low calorie diets should only be considered for adults who need to lose weight rapidly, such as people who need surgery or who are seeking fertility services. People on such a diet should be given ongoing clinical support.

Low calorie diets of between 800 and 1,600 kcal per day can be considered, but NICE say that clinicians should be aware that they are less likely to be nutritionally complete.

What are the implications?

This trial shows that referral from GP practices to a community-based diet replacement programme is very effective in helping people who are obese to lose weight and is associated with other health improvements.

That these effects can be maintained in the longer term is an important finding and suggests that such programmes could be considered routinely for any adults who are obese, not just those who need to lose weight rapidly such as before surgery.

Ongoing support was a feature of the programme used in this trial. NHS funding for such programmes may not be available in all areas of the country. This trial should provide reassurance to those clinicians who are wary about supporting people who choose to use a total diet replacement programme because they are unfamiliar with the approach or have concerns about safety.

This trial used one particular commercial programme providing meal replacement with counselling and support. Similar programmes are available from other providers.

Citation and Funding

Astbury NM, Aveyard P, Nickless A et al. Doctor Referral of Overweight People to Low Energy total diet replacement Treatment (DROPLET): pragmatic randomised controlled trial. BMJ. 2018;362:k3760.

This project was funded by the National Institute for Health Research Collaboration for Leadership in Applied Health Research and Care Oxford, and a research grant from Cambridge Weight Plan UK.



NHS Digital. Statistics on obesity, physical activity and diet – England, 2018 [PAS]. Leeds: NHS Digital; 2018.

NHS website. Obesity – treatment. London: Department of Health and Social Care; 2016.

NICE. Obesity: identification, assessment and management. CG189. London: National Institute for Health and Care Excellence; 2014.

Produced by the University of Southampton and Bazian on behalf of NIHR through the NIHR Dissemination Centre


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