Women at higher risk of breast cancer lost almost 11 kg in 12 weeks on shakes and vegetables. A year later most were still about 8 kg down, though only 4 of 47 had signed up to lower their cancer risk

Carrying excess weight is one of the few risk factors for breast and womb (endometrial) cancer that a person can change, and studies suggest that losing 10% of body weight or more may matter more than smaller losses. Weight-loss surgery delivers that, but it is not something most people want or that health services can offer widely. A team at Manchester University NHS Foundation Trust and the University of Manchester tested a less drastic route: total diet replacement, in which ordinary meals are swapped for nutritionally complete shakes for a few months. Their report on how women coped with a year of it was published in BMJ Open on 28 September 2026.

The 47 women were aged 30 to 50, premenopausal and living with obesity (median BMI 35.9), and all were at increased risk of breast or endometrial cancer; most were recruited through a family-history breast cancer clinic. For 12 weeks they had about 850 kcal a day: three meal-replacement sachets plus five to eight portions of non-starchy vegetables. Over the next four weeks food came back in steps, from 1,000 to 1,500 kcal a day, and for the rest of the year they followed a portion-controlled Mediterranean-style diet, either every day or with one or two 850 kcal days a week. Support came remotely through an app and video or phone calls with a dietitian, with a psychologist for those who needed one. Anyone who regained 2 kg or more could go back on the shakes for two weeks.

Weight fell quickly and much of the loss lasted. The median woman weighed 98.3 kg at the start and was 10.8 kg lighter at three months, 11.5 kg lighter at six months and 8.4 kg lighter at 12 months, with waists about 13 cm smaller. At a year, 46% of the women still in the programme had lost at least 10% of their starting weight. They kept to the low-calorie days 93% of the time; birthdays, religious festivals, holidays, illness and stress were the usual reasons for a day off. Scores for weight-related quality of life and binge eating improved, while scores for depression, anxiety and physical activity did not change.

The harder parts were just as clear. Nineteen women (40%) needed at least one reset after regaining weight, most often between months six and nine. The resistance exercise plan, meant to protect muscle, was largely ignored: the median was zero sessions a week, and the women lost about 2.4 kg of fat-free mass by 12 months. Most joined to lose weight or gain energy; only four named lowering their cancer risk. The study had no comparison group for the full year (a delayed-start group served as controls only for the first three months), the women were mostly White British and well educated, and its main aim, changes in breast and womb tissue, will be reported separately. The authors say controlled trials with longer follow-up are needed before such programmes become routine in cancer-risk clinics.