Why weight gain is not always about eating less and moving more.

Most people who struggle with their weight have already tried eating less and moving more, often more than once. When the weight comes back, or never shifts at all, it is easy to blame a lack of discipline. Yet appetite, the energy burned at rest, where fat is stored and how much muscle is kept are all controlled by hormones, sleep, stress and medicines.

Many people have never been told this: it is not your fault. We are descended from ancestors who were very good at storing energy, because that is how they survived times of scarcity. We now live in a time of abundance, and the same efficient biology works against us. That is not a reason to do nothing. It is a reason to stop blaming willpower and look at the systems that can be measured and changed.

Insulin resistance: the hidden driver.

Insulin moves sugar out of the blood and into muscle and liver after a meal. When those tissues stop responding properly, the pancreas makes more insulin to keep blood sugar normal. This insulin resistance can be present for years before blood sugar rises enough to be called prediabetes, and high insulin makes fat easier to store and harder to burn. Where fat is stored matters more than how much there is. Fat under the skin of the hips and thighs is relatively harmless, but when that store is full, fat overflows into the liver, muscle and the space around the organs, where it drives insulin resistance directly.

The clues are often in plain sight: a waist of 94 centimetres or more in men or 80 in women, raised triglycerides, low HDL cholesterol, mildly raised liver enzymes, rising blood pressure and a family history of diabetes. Together they tell a more reliable story than any single number.

This is more reversible than most people think. In the DiRECT trial, people who had had type 2 diabetes for up to six years followed a weight-management programme in primary care, and after a year 46 per cent were in remission, compared with 4 per cent with usual care. Remission depended on the amount of weight lost.

Food without dogma.

There is no single correct diet. We ask people to pull at least one lever that suits them: eating a little less, cutting back on refined carbohydrate, or narrowing the hours in which they eat, while avoiding ultra-processed food. The shorthand is simple: don’t poison yourself. A study of 800 people and almost 47,000 meals found that the same food produced very different blood sugar responses in different people. Bread is one of the hardest habits to change, but it takes only about two months to wean yourself off it, and few people go back.

Testosterone, thyroid and medicines.

In men, weight and testosterone pull each other down. Fat converts testosterone into oestrogen, insulin resistance lowers SHBG, the protein that carries testosterone in the blood, and inflammation and sleep apnoea suppress the signal to the testes. Low testosterone then makes fat easier to gain and muscle harder to build.

The cycle can be reversed. A meta-analysis of 24 studies found that weight loss raised testosterone, and the more weight was lost, the bigger the rise. For a man carrying extra weight, a low result is a reason to look at weight, sleep and alcohol, and to repeat the test fasting in the early morning, before any decision about treatment. The thyroid is worth checking, but a borderline TSH often rises with weight and settles with weight loss, and thyroid hormone is not a weight-loss treatment.

Keep the muscle.

The scales cannot tell fat from muscle. Visceral fat, stored deep around the organs, is the type most closely linked to diabetes, fatty liver and heart disease, and a waist measurement or a DEXA scan, a low-dose X-ray that measures fat, muscle and bone, shows it far better than body weight. Muscle is where most sugar goes after a meal, and it is easily lost during dieting. The aim is to lose fat while keeping muscle: lose about half a kilogram to a kilogram a week, eat enough protein across three or four meals, and lift at least twice a week. That means picking up something heavy, not only walking. A meta-analysis of 49 trials found that extra protein increased muscle and strength gains up to about 1.6 grams per kilogram a day.

When medical help makes sense.

For some people, lifestyle changes alone are not enough, and that is not a personal failure. Medical options include medicines that act on appetite hormones, meal replacement programmes and surgery. The principle still applies: base first, then we can get fancy. Sleep apnoea, thyroid problems and weight-promoting medicines are dealt with first, and protein and lifting are protected during treatment, because much of the weight lost on appetite medicines can be muscle.