Excess weight and health: what risks are confirmed

This topic is usually presented in a way meant to induce fear. Fear works poorly: it makes people postpone doctor visits rather than change their habits. Below is what is known, without the alarmism.

How excess weight is measured

The primary tool is the body mass index (BMI): weight in kilograms divided by the square of height in meters. A range of 18.5–24.9 is considered normal, 25–29.9 is overweight, and 30 or higher is obesity.

BMI was designed to describe population groups, and it makes predictable errors when applied to an individual. It does not distinguish between muscle and fat, does not know where that fat is located, and is less accurate for the elderly, athletes, and people of different ethnic backgrounds. Therefore, it is supplemented with waist circumference rather than used as a final verdict.

What is associated with excess weight

Associations that are replicated in large studies and are therefore considered reliable:

• Type 2 diabetes — this has the strongest association of all.
• High blood pressure, lipid metabolism disorders, coronary heart disease.
• Fatty liver disease.
• Obstructive sleep apnea.
• Osteoarthritis of the knees and hips.
• A number of cancers: excess adipose tissue is classified by experts as a factor associated with an increased risk of more than a dozen types of cancer.

This list requires caveats. Risk increases gradually, rather than switching on when crossing the 30 mark; an association found at the group level does not predict the fate of a specific individual; almost all of the listed conditions have other risk factors that act independently of weight.

On mortality and the "obesity paradox"

Publications occasionally appear suggesting that with a slight excess of weight, mortality is not higher and is sometimes lower. The explanation is largely technical: the low-weight group often includes smokers and people who have lost weight due to an existing illness. Their increased mortality is attributed to low weight, even though the cause is the reverse. In studies that account for this more carefully, the "paradox" largely disappears.

The reverse error is also common: assuming weight is the only thing that matters. Physical fitness is significantly associated with health and mortality independently of body mass. An overweight person who walks and exercises regularly is in a better position than a sedentary person with a normal BMI.

How much weight do you need to lose for it to matter

Less than is commonly thought. A weight reduction of 5–10% noticeably improves blood pressure and markers of carbohydrate and lipid metabolism — that is, it changes the very numbers for which weight is discussed in the first place. At a weight of 95 kg, this is 5–9 kilograms, not "minus thirty."

The most famous example is the American Diabetes Prevention Program: in people at high risk, dietary changes and physical activity resulting in a weight loss of approximately 7% reduced the incidence of type 2 diabetes more effectively than the medication used for comparison.

From this comes a practical conclusion that diverges from the "all or nothing" logic: the goal is not an ideal weight, but the first few percentage points and maintaining them.

Why fear-mongering does not work

Shame and fear do not lead to weight loss. What they do reliably is cause people to postpone doctor visits, avoid weighing themselves, and quit after the first setback. People who face judgment due to their weight seek medical help less often, and this worsens their health in itself, separate from the kilograms.

The opposite works: specific, measurable actions and tolerance for uneven progress. Not "pulling yourself together," but a small calorie deficit, enough protein, two strength training sessions a week, and sleep. A boring list, but a doable one.

Where to start

With two measurements and one week of observation: weight, waist circumference, and an honest record of what is eaten on typical days. From there, it becomes clear where the starting point actually is — and decisions are made based on facts, not on the feeling that "something needs to be done."

Count it from a photo

Frequently asked questions

How much does excess weight increase the risk of disease?

The risk increases gradually with weight, rather than appearing once a certain number is crossed. The strongest link is with type 2 diabetes; links to blood pressure, lipid metabolism disorders, heart disease, fatty liver disease, sleep apnea, osteoarthritis, and a number of cancers have also been confirmed. A group-level association does not predict the outcome for a specific individual.

Is body mass index accurate?

As a screening tool for groups, yes; for an individual, it is limited. BMI does not distinguish between muscle and fat, does not account for fat distribution, and is less effective for the elderly, athletes, and people of different ethnic backgrounds. Therefore, it is supplemented with waist circumference.

Is it true that people with a slight excess weight live longer?

Such results are mainly explained by a methodological issue: the low-weight group includes smokers and people who have lost weight due to illness, and their mortality is mistakenly attributed to low weight. In studies that account for this, the effect largely disappears.

How much weight do you need to lose to improve health markers?

5–10% of body weight is enough to noticeably improve blood pressure and markers of carbohydrate and lipid metabolism. For a weight of 95 kg, this is 5–9 kilograms. What matters more is whether the result is maintained, rather than how large it is.

Read next

• Visceral fat: why it matters and how to measure it — Two people at the same weight, with the same BMI, can carry very different metabolic risk.
• How caloric intake affects health — Caloric intake answers one question: how much of you there will be.
• How to lose weight correctly — Weight loss is boring: a slight energy deficit, enough protein, strength training, and time.

This article is for general information. It is not medical advice, a diagnosis, or a prescription for treatment or a diet, and it does not replace a consultation with your doctor. If you have a health condition, are pregnant, take medication, or follow a diet prescribed to you, decisions about food belong with your doctor.

Figures from regulations, guidelines and studies are given as they stood when this article was prepared and may since have changed; check them against the primary sources. This article is not advertising, an offer, or individual advice, and neither the author nor the site owner is responsible for decisions taken on the basis of it.