Exercise did not keep lost weight off, but meal replacements did

Losing weight quickly is, paradoxically, the easier half of the problem: very-low-calorie diets reliably strip off kilograms, but most of that loss tends to creep back. What happens in the months after the diet ends is where obesity treatment succeeds or fails, yet maintenance strategies get far less attention than the diets themselves. This review asked a direct and practical question: after an initial period on a very-low-calorie or low-calorie diet, which follow-on strategies actually help people keep the weight off?

The authors systematically searched MEDLINE, the Cochrane Controlled Trial Register and EMBASE from 1981 to 2013 for randomised controlled trials of maintenance strategies following a diet period of under 1000 kcal per day. Twenty studies with 27 intervention arms and 3,017 participants were included, spanning anti-obesity drugs, meal replacements, high-protein diets, dietary supplements, other diets and exercise. During the initial diet phase, participants lost a pooled average of 12.3 kg over a median of 8 weeks.

Compared with controls, anti-obesity drugs improved weight-loss maintenance by 3.5 kg over a median of 18 months, meal replacements by 3.9 kg over a median of 12 months, and high-protein diets by 1.5 kg over a median of 5 months. The two strategies that failed to show significant benefit were exercise, at 0.8 kg with a range that included zero, and dietary supplements, at exactly 0.0 kg. The pattern is striking: every strategy that worked operated through what people ate or through medication, while supplements did nothing at all.

This challenges the intuitive assumption that exercise is the natural guardian of a new, lower weight. It does not show exercise is useless, since only five arms with 347 participants tested it and a small benefit could have been missed, but it does show the confident version of that claim was not supported. The clear winners were dietary structure and pharmacology, which fits the broader evidence that regain is driven primarily by energy intake. How these strategies combine, and what happens beyond the trial durations, remain open questions.

If you are planning or finishing a period of rapid weight loss, the message is that the maintenance phase deserves as much design as the diet itself, and that the design should centre on how you will eat. Structured approaches such as meal replacements and higher protein intakes had measurable protective effects here; generic dietary supplements had none whatsoever. Exercise carries many benefits this review did not measure, but preserving a crash-diet loss was not demonstrably one of them.