Body Mass Index (BMI)


BMI (Body Mass Index) is important as it is widely regarded that your chances of having a longer and healthier life are improved if you have a healthy BMI.

If your BMI is high, you may also have an increased risk of developing type 2 diabetes, as well as other metabolic diseases such as hypertension, high cholesterol and heart disease.

Relationship of BMI with diabetes

Research shows strong links between a high BMI and type 2 diabetes, with the risk of the condition rising with each increase in BMI.

Data studies

A review of over 12,000 people in the United States, published in 2014, showed that people with a BMI of 25-29.9 had a 50% increased risk of diabetes compared to people with a BMI of 18.5-24.9.

Obesity was linked with increased rates of diabetes between 2.5 and 5 times higher than people of normal weight, with the highest risk being those with a BMI of 40 or more. The results found:

  • BMI 25-29.9 (overweight): 50% higher type 2 diabetes risk
  • BMI 30-34.9 (obesity class I): 2.5 times more likely to get diabetes
  • BMI 35-39.9 (obesity class II): 3.6 times more likely to get diabetes
  • BMI 40+ (obesity class III): 5.1 times more likely to develop diabetes

BMI and other long term health risks

The World Health Organisation (WHO) lists a high BMI as a major risk factor for heart disease, stroke, bone and joint problems including osteoarthritis and a number of cancers, including breast, colon and endometrial cancer.

Large scale surveys, such as SHIELD (Study to Help Improve Early evaluation and management of risk factors Leading to Diabetes), conducted in the USA in 2004, show clear associations between a raised BMI and increased risks of hypertension (high blood pressure) and dyslipidaemia (high cholesterol) in addition to type 2 diabetes.

How health care professionals use BMI Formula

BMI is checked regularly by doctors to assess if people are at a healthy weight, with advice dependent on what your BMI reading is:

  • Below 18.5 BMI: advised to eat more to gain weight within a normal range
  • Between 18.5-25: you are of normal weight
  • Between 25-30 BMI: advised to lose weight and exercise more to reduce risk of obesity
  • Over 30 BMI: specific diets and weight loss programmes suggested, as well as referral to a dietitian.

Diet and weight loss programmes

If you have a BMI over 30, you may need to start a weight loss program or given exercise on prescription.

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