Overview
Obesity means carrying enough extra body fat to affect health. It is now understood as a chronic, relapsing disease that arises from the interaction of genetics, the way the brain regulates appetite, eating behaviour, access to affordable healthy food, and the wider environment.
Because it is a medical condition rather than a personal failing, it responds to treatment and support. Losing a modest amount of weight and keeping it off improves , blood sugar, and joint pain.
Symptoms
Obesity is measured rather than felt, but many people notice its effects day to day:
- Getting out of breath easily
- Tiredness during the day
- Difficulty with physical activity or moving about
- Joint and back pain
- Snoring, or poor sleep
- Low self-esteem, low mood or anxiety
When to see a doctor
Otherwise, see a doctor if you are becoming breathless or tired with ordinary activity, if joint pain is limiting you, if you have symptoms that could be diabetes, or simply if you want help with weight.
Causes
Weight rises when the body takes in more energy than it uses, but what drives that balance is complex. Genes affect appetite and how the body stores fat. Poor sleep, stress and low mood change eating patterns.
Some medicines, including certain steroids and antidepressants, can cause weight gain, and conditions such as an underactive thyroid and polycystic ovary syndrome contribute. The food available near us, long working hours and little chance to be active matter just as much.
Risk factors
- A family history of obesity
- Diets high in fried food, refined flour and sugary drinks
- Little physical activity, and long periods sitting
- Poor or short sleep
- Stress, low mood and some mental health conditions
- Certain medicines and hormone conditions
- Disability or illness that limits movement
Complications
- Type 2 diabetes
- High
- Heart disease and stroke
- Several cancers
- Osteoarthritis, especially of the knees and hips
- Fatty liver disease
- Breathing problems during sleep
- Low mood, anxiety and the effects of being judged for weight
Prevention
- Eating more vegetables, fruit, pulses and whole grains
- Cutting down on sugary drinks and fried or heavily processed food
- Being physically active most days, and sitting less
- Getting enough sleep
- Limiting screen time, particularly for children
Diagnosis
A doctor will weigh you, measure your height and work out your body mass index. For most adults, a of 25 to 29.9 is overweight and 30 or above is obesity. For people of South Asian, Chinese, other Asian, Middle Eastern, Black African and African-Caribbean backgrounds, lower thresholds are used: 23 to 27.4 for overweight and 27.5 or above for obesity.
BMI does not show where fat is carried, so waist size is measured too. A simple guide is to keep the waist to less than half your height. Blood tests for sugar, , liver and thyroid are often done as well.
Treatment
The starting point is support to change eating and activity in a way that can be kept up, often through a structured weight management programme with a dietitian or a group. Talking therapies can help where eating is tied to stress or mood.
Medicines are available for some people alongside these changes. Weight loss surgery, also called bariatric or metabolic surgery, is considered when is high and other approaches have been tried, with lower thresholds for the backgrounds listed above. It needs lifelong follow up.
Treating the conditions that come with obesity, such as diabetes, and joint pain, is part of care from the start.
Myths and facts
Things people often say about this. Open each one to see what is true.
Myth“Obesity is simply a lack of willpower.”What is true?
Fact
Health authorities describe obesity as a chronic, relapsing disease that comes from the interaction of genes, the way the brain controls appetite, eating patterns, sleep, some medicines and health conditions, and the food and activity options around us. Blaming willpower is both unkind and unhelpful.
Myth“The same BMI numbers apply to everyone.”What is true?
Fact
Health problems linked to weight appear at a lower BMI in people of South Asian, Chinese, other Asian, Middle Eastern, Black African and African-Caribbean backgrounds. Health services therefore use lower thresholds for these groups: 23 to 27.4 counts as overweight and 27.5 or above as obesity.
Myth“A chubby child is a healthy child who will grow out of it.”What is true?
Fact
Childhood obesity raises the chance of type 2 diabetes and heart and blood vessel disease, can affect a child's wellbeing, and makes obesity in adult life more likely. Helping the whole family eat well, limit sugary drinks and screen time, and stay active is better than waiting.
Myth“Weight loss surgery is the easy way out.”What is true?
Fact
Surgery is considered when BMI is high and other approaches have not worked, and it is a major operation with risks. It changes how the stomach and gut handle food, and it works alongside changes to eating and activity and long term follow up, not instead of them.
Questions to ask your doctor
Tick the ones you want answered and take them with you.
Common questions
How much weight do I need to lose for it to help?
Less than people expect. Losing a small share of body weight and keeping it off improves blood sugar, blood pressure, cholesterol and joint pain. Steady change that you can maintain is worth more than rapid loss that comes back.
Is BMI accurate for everyone?
It is a useful guide, not a diagnosis. It does not distinguish muscle from fat, so it can be misleading for very muscular people, and it says nothing about where fat is carried. That is why waist measurement and blood tests are used alongside it, and why lower thresholds apply for several ethnic groups.
Could a thyroid problem be causing my weight gain?
An underactive thyroid can contribute to weight gain, and it is usually easy to check with a blood test. It is rarely the whole explanation, so treating it is one part of a wider plan rather than a complete answer.
