What Is Obesity? Causes, Risks And Why It's More Than Weight

When someone says the word obesity, it often comes with a lot of emotions.

For some people it’s a diagnosis they’ve recently been given by their GP. For others it’s a word they’ve spent years trying to avoid hearing. It can feel upsetting, embarrassing or even unfair, especially if you’ve spent years dieting without lasting success.

I know that feeling.

For a long time, I believed what so many of us are told – that obesity simply meant I lacked willpower. If I could just eat less, move more and try harder, everything would fall into place.

The more I’ve learnt over the years, the more I’ve realised just how wrong that idea is.

Obesity is a complex medical condition. It’s influenced by far more than the food on your plate, and understanding that can be the first step towards letting go of some of the guilt many people carry.

What does obesity actually mean?

Obesity is a long-term health condition where a person has excess body fat that may increase their risk of certain health problems.

It’s important to remember that obesity is not a judgement about someone’s character, intelligence or worth. It’s simply a medical term used to describe a health condition.

Just as someone can be diagnosed with asthma, arthritis or high blood pressure, obesity is another condition that healthcare professionals assess and treat.

That doesn’t mean everyone with obesity is unhealthy, just as not everyone in a smaller body is automatically healthy. Health is influenced by many different factors.

How is obesity measured?

The most common way obesity is measured is by Body Mass Index (BMI).

BMI compares your height and weight to estimate whether your weight falls within certain categories.

For adults in most cases:

Under 18.5 – Underweight
18.5 to 24.9 – Healthy weight
25 to 29.9 – Overweight
30 or above – Obesity

BMI is useful because it’s quick and easy, but it isn’t perfect.

It doesn’t tell us:

How much of your weight is muscle.
Where fat is stored on your body.
Your fitness level.
Your overall health.
Your lifestyle.
Your medical history.

That’s why doctors usually look at much more than BMI when assessing your health. I wrote about my experience with BMI and why I think there is more to size than BMI after I lost 10 stone and still could have lost weight and had a normal BMI but already looked too thin.

Why do people develop obesity?

This is probably the biggest misconception. Many people believe obesity is simply caused by eating too much and not exercising enough. While food and activity are important, they’re only part of the picture. Obesity develops because of a combination of factors, which may include:

Genetics

Some people are naturally more likely to gain weight than others. Our genes influence appetite, metabolism, fat storage and even how full we feel after eating.

Hormones

Hormones help regulate hunger, fullness and how our bodies use energy.

Conditions affecting hormones, menopause and some medications can all make weight management more difficult.

Mental health

Stress, anxiety, depression and trauma can all affect eating habits.

Many people, myself included, have used food for comfort at different times in life.

Food environment

Highly processed foods are inexpensive, widely available and heavily marketed.

When busy lives are combined with easy access to calorie-dense foods, maintaining a healthy weight becomes much more challenging.

Sleep

Poor sleep can affect the hormones that regulate hunger and appetite, making it easier to overeat without even realising it. I wrote about sleep and weight loss, so this might be of interest to you if you think it is affecting you.

Medical conditions and medication

Some health conditions and medications can contribute to weight gain or make losing weight much harder.

None of these factors means weight loss is impossible, but they do help explain why it isn’t as straightforward as many people think.

Is obesity a disease?

Many health organisations now recognise obesity as a chronic disease. That doesn’t mean it’s contagious or that there’s a single cure.

Instead, it acknowledges that obesity is a long-term condition that often requires ongoing management, just like asthma or diabetes. For some people, lifestyle changes are enough. Others may benefit from medication, psychological support or bariatric surgery.

There’s no single approach that works for everyone.

What health problems can obesity increase the risk of?

Not everyone with obesity will develop health problems, but carrying excess body fat can increase the risk of conditions such as:

Type 2 diabetes
High blood pressure
Heart disease
Stroke
Sleep apnoea
Certain cancers
Osteoarthritis
Fatty liver disease

The risk often depends on several factors, including age, genetics, where body fat is carried and overall lifestyle.

Obesity isn’t just about physical health

This is something that’s often overlooked. Living with obesity can affect much more than your body.

It can influence confidence, relationships, mental health, work, travel and even whether you feel comfortable going to the gym or sitting in a restaurant booth.

Many people experience stigma or feel judged simply because of their size. Sadly, those experiences can make it even harder to ask for help or believe lasting change is possible.

My experience with obesity

I’ve lived with obesity for much of my adult life. I’ve lost 10 stone then regained weight. I’ve felt proud, ashamed, determined and completely exhausted by dieting.

I’ve been through the bariatric surgery pathway before deciding it wasn’t the right choice for me, and I’ve also tried weight loss medication.

If there’s one thing I’ve learnt, it’s that obesity is never as simple as outsiders often think. I’ve met people who exercise every day and still struggle with their weight and people who barely think about food.

I’ve learnt about food noise, emotional eating and how much hormones, stress and life experiences can influence our relationship with food. That’s why I believe kindness is a far better starting point than blame.

Can obesity be treated?

Yes. Treatment isn’t about finding the perfect diet. It’s about finding an approach you can realistically maintain.

That might include:

Gradually improving eating habits.
Becoming more active in ways you enjoy.
Managing emotional eating.
Improving sleep.
Seeking medical advice.
Weight loss medication such as GLP-1 medicines where appropriate.
Bariatric surgery for some people.

The right treatment is different for everyone.

Where should I start?

If you’ve recently been told you have obesity, try not to panic. You don’t need to overhaul your entire life overnight.

Start by understanding your body and your habits rather than chasing another quick fix. Small changes really do add up over time. Most importantly, remember that having obesity does not define who you are.

It doesn’t make you lazy. It doesn’t mean you’ve failed. It simply means you’re dealing with a complex health condition, and like any other condition, you deserve support, evidence-based information and compassion rather than judgement.

Trusted sources and further information

I’ve shared my own experiences throughout this article because I know how valuable it can be to hear from someone who has been there. However, everyone’s situation is different, and it’s always worth looking at trusted medical advice alongside personal stories.

If you’d like to learn more about obesity, these organisations provide evidence-based information:

NHS

The NHS explains what obesity is, how it is measured, the health risks associated with it and the treatments available. You’ll also find practical advice on healthy eating, physical activity and accessing support if you’re worried about your weight.

NICE (National Institute for Health and Care Excellence)

NICE produces the guidance used by healthcare professionals across England. Their recommendations cover the prevention and management of overweight and obesity, including lifestyle support, weight loss medications and bariatric surgery.

British Dietetic Association (BDA)

The British Dietetic Association provides reliable nutrition advice written by registered dietitians. Their resources can help you make informed choices about healthy eating without relying on fad diets or misinformation.

Obesity UK

Obesity UK is a charity run by people with lived experience of obesity. They offer support, information and campaigns aimed at reducing the stigma that many people living with obesity experience.

Remember…

The internet is full of conflicting advice about weight loss. If something sounds too good to be true, promises rapid results or tells you that one food, supplement or diet is the answer for everyone, it’s worth approaching it with caution.

Obesity is a complex condition, and there is no one-size-fits-all solution. What works for one person may not work for another, and that’s perfectly normal.

If you’re concerned about your weight or your health, your GP or another healthcare professional can help you explore the options available and find an approach that’s right for you.

What Is Obesity? Understanding the Condition Without the Judgement

What does obesity actually mean?

How is obesity measured?