Meal replacements beat food-only diets by just over a kilo

Pre-diabetes and the features of metabolic syndrome mark a fork in the road: lose weight and risk falls, drift on and type 2 diabetes and heart disease become more likely. Weight loss is the main lever, and meal replacements, in the form of shakes, soups and bars, are one of the most heavily marketed ways to achieve it. The question that matters is not whether they help people lose weight, but whether they beat a conventional food-based weight loss diet, which is cheaper and arguably easier to sustain. This review pitted the two approaches directly against each other in this at-risk group.

The researchers searched MEDLINE, EMBASE and the Cochrane Library through January 16, 2024 for randomised controlled trials comparing meal replacements, used as part of a weight loss intervention, against conventional food-based weight loss diets in people with pre-diabetes and features of metabolic syndrome. Ten trials with a combined 1254 participants met the eligibility criteria. Results were pooled as mean differences across body weight, body mass index, waist circumference, HbA1c, cholesterol measures and blood pressure, and the overall certainty of the evidence was graded using the GRADE system.

Meal replacements produced greater reductions in body weight, by 1.38 kg beyond conventional diets, along with a 0.56 kg/m2 larger drop in body mass index and 1.17 cm more off the waist. HbA1c fell by an extra 0.11%, LDL cholesterol by 0.18 mmol/L, non-HDL cholesterol by 0.17 mmol/L, and systolic blood pressure by 2.22 mmHg. The authors describe the weight, BMI and cholesterol reductions as small but important, while the extra changes in waist circumference and HbA1c were judged trivial. The certainty of the evidence was rated low to moderate owing to imprecision and inconsistency.

This pooling gives structure to a long-running debate about whether meal replacements offer anything beyond a well-constructed ordinary diet, and it lands on a measured answer: yes, but modestly. The advantage is real across several cardiometabolic markers, yet none of the differences is dramatic, and the low to moderate certainty means the estimates could shift with better trials. Open questions include how durable the advantage is and whether it holds outside the structured settings of a trial.

If you are managing pre-diabetes and weighing up weight loss approaches, this is a reason to think meal replacements can add a modest edge over food-only dieting, likely through the structure and portion control they impose. It is equally a reason to keep expectations calibrated: the extra benefit was just over a kilogram of weight and small movements in cholesterol and blood pressure, not a transformation. Both approaches produced improvements; the gap between them was the small part.