What is obesity?
Obesity is a medical condition that results from the accumulation of excess fat in different parts of the body, leading to a negative effect on health.
How is obesity defined?
Obesity is generally defined using the body mass index (BMI), which measures the relationship between a person’s weight and height.
| Group | BMI |
| Healthy weight | 18.5 – 24.9 kg/m2 |
| Overweight | 25 – 29.9 kg/m2 |
| Obesity | 30 kg/m2 or above |
In people from ethnic minority backgrounds, for example, Black African, Middle Eastern, South Asian, lower BMI threshold are used.
| Group | BMI |
| Overweight | 23–27.4 kg/m2 |
| Obesity | 27.5 kg/m2 or above |
Note: Although easy to measure and widely used, BMI is not a perfect measure of body composition because it doesn’t differentiate between muscle and fat.
What causes obesity?
Obesity has often been misunderstood and oversimplified as a lifestyle choice. We now know it is a complex health condition shaped by many factors outside a person’s control. Our appetite, weight, and metabolism are influenced by genetics, biology, environment, mood, age, mobility, underlying health conditions, and more. Recognising this complexity doesn’t take away personal responsibility; rather, it highlights that our choices are shaped by many factors and that weight is not simply about willpower. People of all shapes and sizes deserve to be treated with compassion, understanding, and respect.
Diet, Psychology and Lifestyle
There is no good evidence that one specific diet is better than another for long-term weight loss. However, different diets work better for different people. A review by a dietitian may help identify the best diet for an individual.
Understanding the psychological side of weight is an important part of effective care. Our thoughts, emotions, stress levels and past experiences can all influence eating habits, motivation and overall wellbeing, and can also affect how our body responds to treatment.
Exercise is also important to maintain muscle mass during weight loss and to support long-term weight maintenance. Some people may benefit from working with an exercise specialist.
If you are considering working with a private dietitian, psychologist or an exercise specialist, here are a few suggestions:
- Abby Hookey, HCPC Registered Dietitian, BSC (Hons) PGDip, MSc, MRes. Contact: abbyhookey@hotmail.co.uk.
- Jordan Goodchild, BSC (Hons), PGCE, Level 3 Personal Trainer. Contact: thornburyfitness@gmail.com.
- Marie Bird, Nourishwellbymarie, RD BSc (Hons), a State Registered Dietitian.
- Milly Orde, Counselling and Pyschotherapy, BSc (Hons), PGCE, Dip.Couns, MNCPS Acc.
Medical Therapy
Several medications that support weight loss are available in the UK.
Orlistat
Orlistat reduces the amount of fat absorbed from food. It is taken as a tablet with each meal. It works best when combined with a low fat diet. The main side effect is diarrhoea, especially if the diet is rich in fat.
To be used alongside a reduced-calorie diet in people with:
- BMI ≥ 30 kg/m2, or
- BMI ≥ 28 kg/m2 with risk factors such as type 2 diabetes, hypertension, or high cholesterol
To stop treatment if 5% weight loss is not achieved after 3 months.
Wegovy and Mounjaro
Semaglutide (Wegovy) activates the GLP-1 receptor while Tirzepatide (Mounjaro) activates the GLP-1 and GIP receptors. These receptors are located in various parts of the body including the appetite centre in the brain. Stimulating them reduces hunger. Both medications are taken as once weekly injections.
Clinical trials in people with overweight and obesity showed an average weight loss of ~ 15% with Wegovy, and 21 % with Mounjaro. In people with type 2 diabetes, average weight loss is ~ 10% with Wegovy and 15% with Mounjaro. Common side-effects include nausea, vomiting, diarrhoea and constipation.
To be used in addition to diet and increased physical activity in individuals with:
- BMI ≥ 30 kg/m2, or
- BMI ≥ 27 kg/m2 with at least one weight-related co-morbidity
It is recommended to stop the treatment if 5% weight loss is not achieved at 6 months.
What to expect at the Obesity and Metabolism Clinic?
At the obesity and metabolism clinic in Bristol we offer consultant-led, specialist, personalised care for people living with excess weight and obesity.
We assess how excess weight is affecting your health, for example, glucose metabolism (such as diabetes), blood pressure, cholesterol, breathing (such as obstructive sleep apnoea) and hormonal or metabolic issues. We also review your current treatments and how they may be influencing your weight.
We take time to understand your health goals and priorities and discuss whether medical treatment for obesity may be appropriate for you. This includes assessing your eligibility for prescription weight-loss medications, such as weight-loss injections, where clinically appropriate.
We support you to make an informed decision about the most appropriate treatment option for you. If medication is prescribed, we provide private prescriptions and ongoing follow-up, including support with managing side effects and adjusting treatment if needed.
If You Are Considering Bariatric Surgery
Although we do not provide bariatric (weight loss) surgery, we can support you if you are considering this option:
- We offer balanced, unbiased information to help you decide whether surgery is right for you
- We help optimise your medical conditions before surgery
- We provide ongoing medical support after bariatric surgery. This includes advice on vitamin and mineral supplementation, management of medical complications, and medical treatment—where appropriate—to support long-term weight-loss maintenance and optimise medical conditions and metabolic health after surgery.
Our aim is to provide consultant-led, expert, compassionate obesity care that is tailored to you and focused on improving your long-term health.