Obesity

Obesity is not a cosmetic matter and not a failure of willpower. It is a state in which so much body fat has built up that it starts interfering with the work of other organs: it raises blood pressure, disturbs sugar metabolism, loads the joints, gets in the way of breathing during sleep, and affects mood and fertility. The benefit arrives long before any «ideal weight» — it shows up with the first five per cent lost.

When extra weight is called obesity

The simplest measure is body mass index: weight in kilograms divided by the square of height in metres. At 1.70 m and 90 kg that comes to about 31.

• below 18.5 — underweight;
• 18.5–24.9 — healthy weight;
• 25–29.9 — overweight;
• 30–39.9 — obesity;
• 40 and above — severe obesity.

The index has one weak spot: it cannot tell fat from muscle. In a heavily built person it reads high with no excess fat at all; in an older person who has lost muscle it reads low even when fat is excessive. That is why the waist is looked at alongside it. Measure your waist midway between the lowest rib and the top of the hip bone, breathing normally and not holding your stomach in, then divide by your height in the same units. A ratio of 0.5 or more means there is too much fat around the middle even if the index looks respectable. It is that fat, rather than the fat on the hips, that drives diabetes and heart disease.

There is an adjustment for background: in people of South and East Asian, Middle Eastern, African and Caribbean origin complications start at a lower weight, so overweight is counted from an index of 23 and obesity from 27.5. In children these numbers do not apply at all — a child's weight is judged by a paediatrician against growth charts for their age.

Why weight goes up

The mechanism is single: more energy comes in than is spent, and the surplus is stored. Behind that simple sum, though, sit a good many things only partly within one person's control.

• Surroundings. Calorie-dense food is cheaper and easier to get than anything else, and both work and the journey to it are spent sitting down.
• Liquid calories. Fizzy drinks, fruit juice and alcohol barely satisfy hunger yet easily add hundreds of calories a day.
• Inheritance. Genes affect appetite and how quickly fullness arrives; they make losing weight harder, not impossible.
• Sleep and stress. Short sleep and constant tension sharpen the pull towards sugar and fat. That is physiology, not sloppiness.
• Eating to handle feelings. If anxiety or low mood regularly end at the fridge, a diet on its own will not fix it.
• Medicines. Weight gain comes with steroid hormones, some anti-epileptic drugs, certain antidepressants and antipsychotics, and insulin.
• Illnesses. An underactive thyroid, polycystic ovary syndrome, the uncommon Cushing's syndrome, rarer genetic syndromes still, and damage to the hypothalamus.

One thing apart: people usually put on a few kilograms after giving up smoking. That is no reason to go back to cigarettes, whose harm is incomparably greater.

What it threatens and how to spot it

Obesity does not hurt, and that is its trick: the complications gather strength quietly. A list of diseases with no telltale signs is useless, so here are the signs.

• Type 2 diabetes. Thirst, passing water often and especially at night, tiredness, itchy skin, cuts that will not heal, blurring vision.
• High blood pressure. Usually shows nothing at all and is found only by measuring: the monitor is more honest than how you feel.
• Sleep apnoea. Loud snoring with pauses in breathing that others notice, waking up wrecked and with a headache, daytime sleepiness that goes as far as nodding off at the wheel.
• Fatty liver disease. Nearly always silent; found on blood tests and ultrasound, occasionally felt as heaviness under the right ribs.
• Heart and arteries. Breathlessness on effort that used to be easy, a pressing pain behind the breastbone, swollen ankles.
• Joints and back. Pain in the knees and hips, morning stiffness, low back pain.
• Digestion and hormones. Heartburn, gallstones; in women irregular periods and trouble conceiving, in men low testosterone.

The risk of several cancers also rises: bowel, breast after the menopause, womb, kidney and pancreas.

When to see a doctor and what will be checked

The reason to book an appointment is not the number on the scales but wanting to understand what is going on. Do not put it off if weight is climbing fast with no change in what you eat, if the gain comes together with swollen legs and breathlessness, if thirst and night-time trips to the toilet have appeared, if you fall asleep during the day against your will, or if the people you live with say you stop breathing in your sleep.

An ambulance is for the complications: pressing chest pain lasting more than a few minutes, sudden severe breathlessness at rest, sudden weakness in an arm or leg, a drooping face. There the count is in minutes; across most of Europe the emergency number is 112.

At the appointment the doctor will weigh you, measure your height and waist, and ask about your way of life, the medicines you take, how your weight has shifted over the years, what you have already tried and how you get on with food. Then come the tests: fasting glucose or glycated haemoglobin, a lipid profile, liver enzymes, thyroid hormones. Blood pressure is measured with a cuff of the right size — a narrow cuff on a large arm reads falsely high.

The reverse is worth knowing too. There is no need to hunt for a rare hormonal cause in everyone who struggles to lose weight. Those tests make sense when other signs are present: wide purple stretch marks, thinned skin, weak thigh muscles, fat gathered on the trunk with slim limbs. That is what Cushing's syndrome looks like, and no diet will touch it.

Food: what actually moves the weight

Only what you can keep doing for years will work; rigid schemes give a quick drop and an equally quick return. The sensible pace is 0.5–1 kg a week, which means eating roughly 500–600 calories a day less than you spend. The exact figure is better worked out with a doctor or a dietitian.

• Build the plate on vegetables and fruit, wholegrain cereals and bread, and pulses.
• Protein at every meal: fish, poultry, eggs, curd cheese. It satisfies best and protects muscle.
• Less processed food, pastry, fast food, sugary drinks and alcohol — a glass of wine carries the calories of a slice of bread.
• Salt is limited separately from calories, because it pushes blood pressure up.
• Watch the portion: the same food on a smaller plate is fewer calories.

What not to do: fast for days on end, cut out whole food groups, or buy «fat burners». Diets of under 800 calories a day do exist, but they are used on medical grounds and under supervision — taken up alone they cost you muscle and bring on gallstones.

Movement

Losing weight by training alone is hard: food goes on faster than exercise burns it off. Keeping the loss without movement, however, is close to impossible, and blood pressure, blood sugar and mood improve before the scales shift at all.

The guide for adults is 150–300 minutes of moderate activity a week: brisk walking, cycling, swimming, dancing. Moderate means your breathing has quickened but you can still talk; half of that time can be swapped for vigorous activity. Twice a week add strength work, because weight loss takes muscle as well as fat.

Starting with ten minutes and building up gradually is sensible, and breaking up long spells of sitting is a task of its own — get up and walk about at least once an hour. If your joints hurt, you are very breathless or you have heart disease, discuss exercise with your doctor: with bad knees, swimming, water exercise classes and a stationary bike come to the rescue.

Medicines and surgery

Both are considered when food and movement have not produced a result, and always alongside them rather than instead.

Orlistat blocks the absorption of part of the fat in your food. Its effects are predictable — oily stools, urgent trips to the toilet, wind — and the fattier you eat, the stronger they are.

Drugs based on gut hormones — liraglutide, semaglutide, tirzepatide — act on appetite: fullness comes sooner and lasts longer. They are injected under the skin and they genuinely work, but there are caveats. Nausea at the start is common. When they are stopped appetite returns and often the weight with it, so treatment is planned for the long term. With severe vomiting or diarrhoea the contraceptive pill may fail and a backup method is needed; pregnancy is not planned while on treatment. The choice belongs to a doctor: this market is full of counterfeits.

Surgery — reducing the size of the stomach, or a gastric bypass — is discussed in severe obesity and also from an index of 35 when there is an illness that weight loss would improve: diabetes, apnoea, advanced arthritis. It gives the most durable result but commits you to vitamins for life and to regular follow-up. Before any operation or anaesthetic, tell the team you are using weight-loss drugs: they slow the emptying of the stomach.

How to hold on to the result

The body pushes back: the less you weigh, the less energy you spend, so after a few months the loss slows by itself. That is not a failure. What helps you hold on:

• a realistic target — 5–10 % of the starting weight, not «thirty kilograms by summer»;
• weighing yourself in the same conditions each time and keeping short notes of what you eat;
• more movement precisely at the maintenance stage, nearer an hour a day;
• support from family, friends or a group: alone it is harder;
• work with a psychologist if food is how you handle feelings — binge eating disorder is a condition in its own right and it is treatable.

Even 3–5 % of body weight, held for years, noticeably lowers blood pressure, blood sugar and the load on the joints. Putting some of it back happens to almost everyone and means only one thing: return to the plan rather than abandon it.

Online consultation with a doctor

For obesity a remote appointment suits better than it does for many other problems: people come here with questions rather than acute pain. The doctor will go through your test results, weigh up the risks, help build an eating and activity plan that fits your life, explain what to do about medicines that themselves cause weight gain, and set out where things stand with weight-loss drugs. It is also convenient for reporting back: a short conversation every few weeks disciplines better than promises made to oneself.

What it does not replace: blood being taken, blood pressure measured, ultrasound, and assessment before an operation. With breathlessness at rest, chest pain or rapid weight gain with swelling, an in-person visit is needed.

This material is for information only and does not replace medical advice.