Obesity and Overweight in Adults

obesity in adults

If you are obese or overweight, this means that you are carrying excess body fat. Over time, it means that you have an increased risk of developing various health problems.

Body mass index - BMI

BMI is used by healthcare professionals to assess if someone's weight is putting their health at risk. It is a measure of your weight related to your height. To calculate your BMI, you divide your weight (in kilograms) by the square of your height (in metres). So, for example, if you weigh 70 kg and are 1.75 metres tall, your BMI is 70/(1.75 x 1.75), which is 22.9.

BMI Classed As Health Risk
Less than 18.5 Underweight Some health risk
18.5 to 24.9 Ideal Normal
25 to 29.9 Overweight Moderate health risk
30 to 39.9 Obese High health risk
40 and over Very obese Very high health risk
Waist circumference
If you are overweight, measuring your waist circumference can also give some information about your risk of developing health problems (particularly coronary heart disease and type 2 diabetes).

As a rule for a man:

  • If you have a waist measurement of 94 cm or above, the risk to your health is increased.
  • If you have a waist measurement of 102 cm or above, the risk is even higher.

As a rule for a woman:

  • If you have a waist measurement of 80 cm or above, the risk to your health is increased.
  • If you have a waist measurement of 88 cm or above, the risk is even higher.

What are the health risks of being overweight or obese?

  • Feel tired and lacking in energy.
  • Experience breathing problems.
  • Feel that you sweat a lot.
  • Develop skin irritation.
  • Have difficulty sleeping.
  • Get complaints from your partner that you snore.
  • Experience back and joint pains which can affect your mobility.

You may also have an increased risk of developing:

  • Impaired glucose tolerance (pre-diabetes).
  • Type 2 diabetes.
  • High cholesterol or triglyceride levels.
  • High blood pressure.
  • Coronary heart disease.
  • Stroke.
  • Sleep apnoea.
  • Fertility problems.
  • Complications in pregnancy.
  • Stress incontinence.
  • Gallstones.
  • Cancers (including colon, breast and endometrial (womb) cancer).
  • Gout.
  • Fatty liver.

What is the cause of being overweight or obese?

  • If the amount of calories that you eat equals the amount of energy that your body uses up, then your weight remains stable. If you eat more calories than you burn up, you put on weight. The excess energy is converted into fat and stored in your body.
  • What you drink is also important. Alcohol and sugary drinks contain a lot of calories. Even fresh fruit juices that you may think are healthy can make up a significant part of your daily calorie intake if you drink too much of them.
  • A lack of physical activity by many people is thought to be a major cause of the increase in obesity in recent years.
  • You are more likely to be obese if one of your parents is obese, or both of your parents are obese.

Medical problems
Less than 1 in 100 obese people has a 'medical' cause for their obesity. For example, conditions such as Cushing's syndrome and an underactive thyroid are rare causes of weight gain. Women with polycystic ovary syndrome may also be overweight.
Some medicines such as steroids, some antidepressants, sulphonylureas and sodium valproate may contribute to weight gain.

What are the benefits of losing weight and how much weight should I lose?

  • Many people feel better, and have more energy. If your BMI is between 25 to 35, much of the health benefits come with losing the first 5-10% of your weight.
  • You are much less likely to develop the health problems such as diabetes.
  • If you already have problems such as high blood pressure, high cholesterol, osteoarthritis, or diabetes, these are likely to improve.
  • You are less likely to die from heart disease, stroke, diabetes, or obesity- related cancers.

How can I lose weight?

  • Losing weight and then keeping it off, needs a change in your lifestyle for life. This includes such things as:
    • The type of food and drink that you normally buy.
    • The type of meals that you eat.
    • Your pattern of eating.
    • The amount of physical activity that you do.
  • Motivation is crucial: no weight loss plan will work unless you have a serious desire to lose weight.
  • Monitor your current food intake: Keeping a detailed diary of everything that you eat and drink over an average week is helpful.
  • Aim to lose weight gradually: it is best not to lose weight too fast. Aim to lose an average of 0.5 to 1 kg per week.
  • Set clear goals with a realistic timescale.
  • Aim to eat a healthy balanced diet
  • Eat slowly.
  • Don't skip meals.
  • Be careful about what you drink
  • Increase your physical activity levels
    • It is recommended that all adults should aim for at least 30 minutes of moderate-intensity physical activity on at least five days of the week. However, if you are overweight or obese and are aiming to lose weight, if possible you should try to do around 60-90 minutes on at least five days of the week.
  • Monitor your behavior and progress
  • Get help and support

Drug treatment to help with weight loss
There are no wonder drugs available. Lifestyle changes to improve diet and increase physical activity are still important.
The drug orlistat is available on prescription from your doctor.

Surgery to help with weight loss
However, surgery is usually only offered if you have already tried other ways to lose weight which have not worked (including diet, increasing your physical activity levels and orlistat). Surgery usually has very good results and most people do lose a lot of weight.

Keeping the weight off

  • Keeping to a healthy diet.
  • Exercising regularly.
Body Mass Index Calculator
Enter the following data
Sex male female
Body Surface Area m2
Lean Body Weight kg = lbs
Ideal Body Weight kg = lbs
Body Mass Index kg/m2 =
Interpretation of the results
BMI < 18.5 underweight
BMI 18.5 to 24.9 healthy
BMI 25 to 29.9 overweight
BMI 30 or more obese

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