I have sat with patients who have tried every diet, every exercise programme, every intervention — and who describe their inability to sustain weight loss with a shame and self-blame that I find genuinely painful to witness. They have been told, implicitly and explicitly, that their weight is a matter of willpower. That if they just tried harder, wanted it more, chose better — the weight would come off and stay off.
This narrative is not only unkind. It is also wrong.
The science of obesity has advanced significantly in the past two decades. We now understand that body weight is regulated by a complex system of hormones, neural pathways, and genetic factors that actively resist weight loss. We understand that for most people, sustained weight loss through diet and exercise alone is genuinely difficult not because of moral failure but because of physiology. And we are now in the middle of a genuine pharmacological revolution — the GLP-1 agonists — that represents the most significant advance in obesity treatment in decades.
This article is about all of it.
Why "eat less, move more" fails most people
The energy balance equation — calories in minus calories out — is accurate as a description of thermodynamics. As a prescription for long-term weight management, it is profoundly incomplete.
When you lose weight through calorie restriction, your body responds in multiple ways designed to resist that weight loss and restore your previous set point:
Hormonal changes: Leptin (the satiety hormone) falls significantly. Ghrelin (the hunger hormone) rises. This means you feel persistently hungrier after weight loss than before — not because of psychological weakness but because of measurable hormone changes that can persist for years after the weight loss.
Metabolic adaptation: Your resting metabolic rate falls — and falls more than would be expected from the reduced body mass alone. Your body becomes more metabolically efficient, burning fewer calories for the same activities.
Neural changes: Reward pathways in the brain increase their response to food cues. High-calorie foods become more compelling.
These changes — documented in rigorous metabolic studies including the famous Biggest Loser follow-up study, which found persistent hormonal and metabolic adaptations six years after dramatic weight loss — explain why most people who lose weight through diet alone eventually regain it. This is not failure. It is biology.
Case study: David's twelve-year struggle
David, 46, an IT manager from Nigeria based in Manchester, came to see me after twelve years of weight management attempts. He had lost significant weight on four separate occasions — once through a very low calorie diet (40kg in 8 months), once through an intense gym programme (18kg in 6 months), and twice through commercial weight loss programmes. Each time, the weight returned within 18–24 months, often exceeding his starting weight.
His current BMI was 38. He had type 2 diabetes (HbA1c 65), hypertension, and knee pain limiting his exercise capacity. He described feeling "broken" and "unable to understand why I can't do what others seem to manage easily."
I explained the biology. I told him the science. I watched his expression shift from shame to something closer to relief.
"You mean it's not just me?" he said.
No. It is not just him. And there are options now that did not exist when he started this journey.
BMI and Black patients — an important caveat
BMI was developed using predominantly European populations and its relationship to health risk is different across ethnicities. For people of African origin:
- Cardiovascular and metabolic risk may be elevated at lower BMI values than in white Europeans — meaning a BMI of 27 in a Black patient may carry similar metabolic risk to a BMI of 30 in a white patient
- Conversely, Black patients tend to have greater bone density and muscle mass, which increases BMI without reflecting excess body fat
- Waist circumference is a better predictor of metabolic risk in Black patients — above 80cm in women and 94cm in men is considered elevated risk; above 88cm and 102cm respectively is high risk
For these reasons, BMI should be interpreted alongside waist circumference and clinical assessment rather than in isolation.
What actually helps — the evidence hierarchy
Lifestyle intervention: Dietary change and increased physical activity are the foundation of any obesity management approach. The most effective dietary approach is the one a person can sustain — Mediterranean, low-carbohydrate, and low-fat approaches all produce similar long-term results in head-to-head comparisons. The most effective exercise is regular aerobic activity (150+ minutes per week) with resistance training.
Lifestyle intervention alone typically produces 5–10% weight loss over 6–12 months. This is clinically meaningful — 5% weight loss reduces diabetes risk by 58%, reduces blood pressure, and improves metabolic markers significantly. But it frequently does not produce the weight loss people hope for, and maintaining it long-term is genuinely difficult.
GLP-1 receptor agonists — the pharmacological revolution:
Semaglutide (Ozempic for diabetes, Wegovy for obesity) and liraglutide (Victoza for diabetes, Saxenda for obesity) are GLP-1 receptor agonists — medications that mimic a gut hormone that regulates appetite, satiety, and food reward.
The clinical trial results are remarkable:
- Semaglutide 2.4mg weekly (Wegovy): average weight loss of 15% of body weight in the STEP trials — far exceeding anything previously available
- Some patients lose 20–25% of body weight
- Sustained over 2 years of treatment
- The SELECT trial showed significant reduction in cardiovascular events in people with obesity and cardiovascular disease — meaning these drugs do more than reduce weight
Tirzepatide (Mounjaro — also a GIP/GLP-1 agonist): even more impressive results — up to 22% average weight loss in clinical trials.
Side effects: Primarily gastrointestinal — nausea, vomiting, diarrhoea, constipation. Usually most prominent when starting and reducing doses. Generally manageable and reduce over time.
Availability on NHS: Currently available for type 2 diabetes (Ozempic). Wegovy for obesity was approved by NICE in 2023 for specific criteria — BMI above 35 with weight-related comorbidities, or BMI above 30 in certain high-risk groups. Access through specialist weight management services, not standard GP prescribing. Private prescriptions are available but expensive (£200–300/month).
Bariatric surgery: For severe obesity (BMI above 40, or above 35 with significant comorbidities), bariatric surgery — gastric bypass, sleeve gastrectomy, or adjustable gastric band — remains the most effective intervention for long-term weight loss and metabolic improvement. It is not a quick fix — it requires lifelong dietary commitment and monitoring — but results are far more durable than medication or lifestyle alone for people with severe obesity. Available on the NHS for eligible patients through specialist services.
Obesity and mental health — the bidirectional relationship
Obesity and mental health are profoundly interconnected. Depression and anxiety increase the risk of obesity (through effects on appetite, physical activity, stress eating, and medication side effects). Obesity increases the risk of depression (through stigma, physical limitations, metabolic effects on mood, and sleep disruption from sleep apnoea).
Treating obesity without addressing mental health, or treating mental health without addressing metabolic health, produces worse outcomes than addressing both simultaneously. If you are working on your weight and struggling with mood, please bring both to your GP or care team.
The weight stigma problem
Weight stigma — discrimination, prejudice, and negative stereotyping based on weight — is prevalent in healthcare settings, workplaces, and social contexts. Research shows it causes genuine harm: people who experience weight stigma have worse health outcomes, are less likely to seek healthcare, and experience higher rates of depression and anxiety.
Healthcare providers are not immune. Studies show that even doctors hold implicit weight biases that affect how they interact with patients and how quickly they diagnose and treat conditions unrelated to weight.
If you feel your health concerns are being dismissed because of your weight, or that you are experiencing judgement rather than care, you are entitled to say so, to ask for a second opinion, and to expect respectful, evidence-based care regardless of your BMI.
Sources: Sumithran P et al, NEJM 2011 (persistent hormonal changes after weight loss); Fothergill E et al, Obesity 2016 (Biggest Loser follow-up study); Wilding JPH et al, NEJM 2021 (STEP trial — semaglutide); Lincoff AM et al, NEJM 2023 (SELECT cardiovascular trial); Jastreboff AM et al, NEJM 2022 (tirzepatide SURMOUNT trials); NICE NG187 — Obesity: Identification, Assessment and Management (2014, updated 2023).