Bariatric surgery6 min read
What Causes Obesity? The Main Factors Beyond Simply Eating Too Much
Obesity is often explained as a matter of eating too much and moving too little. That is part of the picture, but it does not explain why some people gain weight easily, why lost weight tends to return, or why willpower alone so often fails. This guide explains the main factors doctors recognise today, from appetite hormones and genes to sleep, stress and environment, and what they mean for treatment.
The main points in 30 seconds
- Obesity is a chronic disease with many causes, not simply a lack of willpower.
- Appetite hormones and the body's defence of its weight make lasting weight loss hard.
- Genes, age, sleep, stress and hormonal conditions all influence body weight.
- Hormonal causes such as thyroid problems are checked and treated first.
- For severe obesity with related illness, surgery is usually the most effective treatment.
Key facts about the procedure
- Back to work2–4 weeks
- Stay in clinic1–5 days
- Final result18–24 months
- Price
$4,800from $3,600
What Obesity Means Medically
Doctors define obesity as an excess of body fat that harms health. In practice it is usually measured with the body mass index, or BMI, which relates weight to height. A BMI of 30 or more is classed as obesity, and 40 or more as severe obesity. Waist size adds useful information, because fat stored around the abdominal organs is more closely linked to diabetes and heart disease than fat on the hips and thighs.
Medical organisations now describe obesity as a chronic disease rather than a personal failing. It develops through many interacting factors, tends to persist and needs long-term management, just like high blood pressure or type 2 diabetes.
Energy Balance and Metabolism
At its simplest, weight rises when the body takes in more energy from food and drink than it uses. The body uses energy in three main ways:
- basic functions at rest, such as breathing, circulation and keeping warm, which account for most daily use;
- digesting and processing food;
- physical activity, from walking and household tasks to exercise.
Resting energy use differs between people and depends on body size, muscle mass, age and sex. Muscle uses more energy than fat, which is one reason metabolism tends to slow when muscle is lost with age or inactivity. A small daily surplus, repeated over years, can add many kilograms without any obvious overeating.
Appetite Hormones and Why the Body Resists Weight Loss
Hunger and fullness are controlled by signals between the gut, fat tissue and the brain. Hormones released by the stomach increase hunger before meals, while others released by the intestine after eating create a feeling of fullness. Fat tissue itself sends signals that tell the brain how much energy is stored.
In obesity these signals often work less well: the brain responds weakly to fullness hormones, so more food is needed to feel satisfied. When a person loses weight by dieting, the body reacts as if energy were scarce. Hunger hormones rise, fullness signals fall and resting energy use drops. This protective response explains why most people regain weight after a diet, and why weight loss is not simply a question of discipline.
Blood Sugar, Thyroid and Stress Hormones
Several hormonal conditions influence weight:
- Reduced sensitivity to the hormone that controls blood sugar. When cells respond poorly, the body produces more of this hormone, which promotes fat storage, especially around the abdomen. This state often precedes type 2 diabetes.
- An underactive thyroid. It slows metabolism and can add some weight, usually a few kilograms, mostly from fluid. Treating it helps, but it rarely explains severe obesity on its own.
- Stress hormones. Long-term stress and, rarely, diseases in which the adrenal glands produce too much of their own stress hormone increase appetite and abdominal fat.
- Other conditions. Polycystic ovary syndrome in women and low sex hormone levels in men are linked with weight gain.
Some long-term medicines can also increase appetite or weight. If you suspect this, discuss it with the doctor who prescribed them rather than stopping treatment yourself.
Genetics and Age
Genes strongly influence body weight. Studies of twins and adopted children suggest that a large part of the difference in weight between people is inherited. Most of this comes from many common gene variants, each with a small effect on appetite, fullness and how the body stores fat. Rare single-gene forms cause severe obesity from early childhood.
Genes do not make obesity inevitable, but they explain why two people with similar habits can have very different weights. With age, muscle mass tends to fall and activity decreases, so energy needs drop. In women, the hormonal changes around menopause often shift fat towards the abdomen.
Lifestyle and Environment
Modern surroundings make weight gain easy. Energy-dense, highly processed food is cheap, tasty and available everywhere, portions have grown and many jobs involve sitting most of the day. Other factors add to this:
- short or poor-quality sleep, which increases hunger and cravings;
- sugary drinks and alcohol, which add energy without much fullness;
- eating in response to stress, boredom or low mood;
- stopping smoking, which often leads to some weight gain;
- pregnancy, when weight gained may not be fully lost afterwards.
These influences interact with genes and hormones. That is why effective treatment addresses several factors at once rather than relying only on eating less.
Finding Your Treatment Path at City Medical Centre
Treatment depends on how severe obesity is and which conditions accompany it. For many people it starts with changes to diet, activity and sleep, psychological support and, where appropriate, weight-loss medicines or injections prescribed by a doctor. When obesity is severe or has already led to illness, surgery is usually the most effective option. Hormonal causes are checked and treated by an endocrinologist first.
City Medical Centre performs sleeve gastrectomy, Roux-en-Y gastric bypass, one-anastomosis gastric bypass and SADI-S. It does not prescribe weight-loss injections or place intragastric balloons; whether a gastric band is performed at the clinic is clarified at the consultation. These methods are mentioned here for general information. The first consultation is free and can take place online: share your height, weight, weight history, the conditions you are treated for and recent test results, and the surgeon will assess whether surgery is right for you and which method suits you best. The cost is named after this assessment and fixed in the contract. A personal coordinator supports you throughout, and you can send questions on Telegram. Read more on the bariatric surgery page.
How recovery usually goes
- First hoursYou may sit up, stand and drink fluids
- 1–5 daysObservation at the clinic, depending on the extent of surgery
- 2–4 weeksReturn to office work; physical work after about 1.5 months
- 1–2 monthsStaged diet from liquids to solids to let the stomach adapt
- Every monthOn average 10% of excess weight lost per month
- 1.5–2 yearsFinal result, stable eating habits prevent the weight from returning
Sources
Frequently asked questions
Is obesity genetic?
Partly. Genes have a large influence on appetite, fullness and how the body stores fat, and they explain much of the difference in weight between people. Environment and habits decide how strongly that tendency shows. A family history of obesity means a higher risk, not a fixed outcome.
Can hormones cause weight gain?
Yes. Poor sensitivity to the hormone that controls blood sugar, an underactive thyroid, excess stress hormones, polycystic ovary syndrome and low sex hormone levels in men can all contribute. Blood tests help identify them, and treating the cause is an important part of managing weight.
Why is it hard to keep weight off?
After weight loss the body defends its previous weight: hunger hormones rise, fullness signals weaken and resting energy use falls. This makes regain very common after dieting alone. Long-term support, activity and, for severe obesity, surgery help counter this response.
Does thyroid disease cause obesity?
An underactive thyroid slows metabolism and can add a few kilograms, largely from fluid, but it rarely causes severe obesity by itself. It is easy to check with a blood test, and treatment helps, though weight does not always return fully to previous levels.
When is obesity dangerous?
Risk rises with higher BMI and with fat stored around the waist. Obesity becomes especially dangerous when it comes with type 2 diabetes, high blood pressure, sleep apnoea, fatty liver or joint damage. These are signs to discuss effective treatment with a doctor rather than wait.
Have a question about your case? Get a free consultation
Message a coordinator on Telegram: we reply right in the chat, and you can send photos and questions there too.
- The first consultation is free, online consultations are available
- The doctor names the cost after the assessment, and it is fixed in the contract
- A personal coordinator guides you from the first message to recovery
Message our coordinator on Telegram
We reply right in the chat — you can send photos
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