Exercise in Obesity

It helps to be clear about what activity can and cannot do for weight. On its own, physical activity usually produces only modest weight loss, and dietary change is the stronger driver of losing weight. Where activity earns its place is in improving health independently of weight, and in helping to maintain weight after loss, where higher activity volumes may help, rather than any single universal threshold. A loss of just 5 to 10 percent of body weight already brings meaningful improvements in blood pressure, glucose and other metabolic markers, and activity adds cardiovascular and functional benefits on top. Framing success around fitness, strength, energy and how a person feels, rather than weight alone, is both more accurate and more motivating.

Weight-management medication has changed this landscape. Weight-management medicines such as the glucagon-like peptide-1 (GLP-1) receptor agonist semaglutide, and the dual glucose-dependent insulinotropic polypeptide (GIP) and GLP-1 receptor agonist tirzepatide, produce substantial weight loss, but a proportion of the weight lost is lean mass rather than fat. Resistance training is recommended to support muscle strength and function during weight loss, and the evidence that it shifts the composition of weight loss towards fat is still emerging. A practical approach is resistance work on at least 2 to 3 days a week, alongside at least 150 minutes of aerobic activity, with adequate protein intake individualised to the person, ideally with dietetic input, rather than a single universal target. The same combination of aerobic and resistance activity supports recovery and long-term outcomes after bariatric surgery, where preserving muscle and function matters just as much.

Getting started should be realistic and kind. For someone carrying a lot of weight, joint pain, breathlessness and self-consciousness are common and genuine barriers, so low-impact options that reduce load on the joints, such as water-based exercise, cycling, or seated and supported activity, are a good way in, building up gradually as fitness improves. Any activity counts, and small, achievable goals, like a short daily walk, are more useful than an unrealistic target. Enjoyable and social activities help people keep going, and a supportive, non-judgemental approach from the clinician makes a real difference to whether someone stays active.

• •Much of the benefit of activity in obesity occurs independently of weight change.
• •Activity alone produces modest weight loss; diet is the stronger driver of losing weight.
• •Higher activity volumes may help maintain weight loss after it is achieved.
• •On weight-management medication, a proportion of lost weight is lean mass.
• •Resistance training supports muscle strength and function during weight loss; protein is individualised.
• •Low-impact options and gradual, realistic goals support getting started.