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What exactly is obesity?

Dr. Alexandra Phelan: General Practictioner | minute read
What exactly is obesity?

If you’re struggling with your weight, you’re not alone. According to a 2021 Health Survey for England, more than a quarter (25.9%) of all adults were classed as obese. Some 37.9% were overweight, according to body mass index statistics.

What is the definition of obesity?

The NHS describes obesity as living with excess body fat. Obesity is measured by two key calculations:

  • The body mass index (BMI)

  • The waist to height ratio.

Body mass index

BMI calculations measure your height and weight. They also account for gender, as females tend to carry more body fat than men. Scores generally range from 18 to 40. The ‘healthy weight’ range is anywhere between 18.5 and 24.9. Overweight people range from 25 to 29.9, while an obese weight is classed as anything from 30 upwards.

It’s important to note that this is based on averages. Some people may be very heavy for their height, for example, particularly muscular athletes. Other factors, such as body fat percentage, can give a more accurate reading of obesity.

Waist to height ratio

The waist to height ratio is ideal for adults with a BMI under 35. You should start by measuring your waist. Next, measure your height (make sure you’re using the same units for both, i.e., inches or centimetres).

If your waist circumference is more than 50% of your height (a ratio of 0.5) then you may be considered obese.

What are the health risks of being obese?

Obesity can cause a range of health issues, affecting some people more than others. For example, women face increased risks of breast cancer or stillbirth and miscarriage. Men could encounter fertility problems.

Both men and women are also at increased risk of:

  • Type 2 diabetes

  • Coronary heart disease

  • Hypertension (high blood pressure)

  • High cholesterol

  • Stroke

  • Mental health issues

Maintaining a healthy weight through a balanced diet and physical activity is the best way to prevent adult obesity.

What causes obesity?

The causes of obesity range from genetics to lifestyle and certain health conditions. A person’s weight may increase if they regularly eat high-calorie foods while living a relatively inactive lifestyle. When we eat fatty or sugary foods, we take on glucose. This is stored as fat if we don’t do enough exercise to burn it off.

Ethnic backgrounds

People of Asian, Middle Eastern, Black African or Afro-Caribbean backgrounds may be more prone to obesity as their BMI scores only need to be 27.5 to be classed as obese. Childhood obesity is highest among Black children at 16.2%, while 72% of Black adults and 37.5% of Chinese adults in the UK are overweight or obese.

Underlying health conditions

Medications to manage certain health conditions may cause us to gain weight. Antidepressants, steroids, diabetes, and blood pressure medications have all been reported to cause weight gain in some people.

Some health conditions such as hypothyroidism may also increase the risk of obesity, though this can be managed with medication.

How to prevent and treat obesity

‌While we can’t control our genes, we can make lifestyle changes for better weight management. A healthy lifestyle starts in the kitchen. Limit processed foods and try switching to whole grains, green vegetables and lean protein instead.

The NHS offers ‘healthy swap’ options to replace fast food and high-calorie treats with nutritious alternatives. Around 150 minutes of moderate exercise or 75 minutes of vigorous activity per week can help to maintain a healthy lifestyle.

Weight loss surgery and other treatments

If you have a chronic weight condition, your doctor may recommend other options. You may be offered bariatric surgery if your BMI is over 40 and you’ve tried other weight loss methods unsuccessfully over a long period of time.

This is a major decision, and it is far less risky to manage your activity and calorie intake. Always speak to a dietitian or medical professional if you’d like to reduce your body weight. You may also want to try weight loss supplements alongside a calorie-controlled diet.

Significant weight loss doesn’t happen overnight – you should aim for 1-2 lbs per week. With a long-term commitment, you’ll reduce your risk of many types of cancer, and enjoy a better quality of life.