Body Mass Index (BMI) is a widely used measurement that helps determine whether a person’s weight falls within a healthy range based on their height. However, having a BMI that is too high or too low can increase the risk of several health conditions.
✔ A high BMI (overweight or obese) is linked to heart disease, diabetes, and joint problems.
✔ A low BMI (underweight) may lead to malnutrition, weakened immunity, and osteoporosis.
This guide explores the health risks associated with BMI, NHS-recommended BMI ranges, and how to manage your weight to stay healthy.
BMI is calculated using the following formula:
Metric Formula:
BMI = Weight (kg) ÷ Height (m²)
Imperial Formula:
BMI = (Weight (lbs) ÷ Height (inches²)) × 703
While BMI is a useful indicator of weight-related health risks, it does not differentiate between fat and muscle mass. This means that some people with higher muscle mass (e.g., athletes) may have a high BMI but low body fat.
| BMI Range | Category | Health Risk Level |
|---|---|---|
| Below 18.5 | Underweight | Increased risk of nutritional deficiencies and weak immunity |
| 18.5 – 24.9 | Healthy Weight | Lowest health risks |
| 25 – 29.9 | Overweight | Moderate risk of chronic diseases |
| 30 and above | Obese | High risk of serious health conditions |
✔ Weakened immune system – Higher susceptibility to infections.
✔ Nutritional deficiencies – Low levels of vitamins and minerals can cause hair loss, skin problems, and fatigue.
✔ Osteoporosis and fractures – Low bone density increases the risk of fractures.
✔ Loss of muscle mass – Weak muscles can affect mobility and strength.
✔ Irregular menstrual cycles – Hormonal imbalances may lead to infertility.
✔ Higher risk of pregnancy complications – Including premature birth and low birth weight.
✔ High blood pressure (hypertension) – Can lead to heart disease and stroke.
✔ Type 2 diabetes – Overweight individuals are at greater risk of insulin resistance.
✔ Sleep apnoea – Excess weight can cause breathing difficulties during sleep.
✔ Joint and back pain – Extra weight increases strain on joints and the spine.
✔ Higher risk of anxiety and depression.
✔ Lower self-esteem and body confidence due to weight stigma.
✔ Heart disease and stroke – Due to high cholesterol, high blood pressure, and blocked arteries.
✔ Type 2 diabetes – Excess weight increases insulin resistance, raising blood sugar levels.
✔ Cancer risk – Obesity is linked to a higher risk of breast, colon, and liver cancer.
✔ Fatty liver disease – Excess fat accumulation in the liver can lead to liver damage.
✔ Kidney disease – Increased strain on kidneys may cause kidney failure.
✔ Reduced mobility and difficulty performing physical activities.
✔ Higher risk of mental health issues, including depression and social anxiety.
✔ Lower life expectancy due to increased risk of chronic diseases.
People with a BMI over 25 have a higher risk of heart disease, heart attacks, and stroke.
High cholesterol and high blood pressure are more common in overweight individuals.
Obesity is the biggest risk factor for Type 2 diabetes.
Losing 5-10% of body weight can improve blood sugar control.
✔ Eat whole foods – fruits, vegetables, lean proteins, and whole grains.
✔ Limit sugar, processed foods, and unhealthy fats.
NHS Meal Plans for a Healthy BMI
✔ Aim for 150 minutes of moderate exercise per week (e.g., brisk walking, cycling).
✔ Include strength training to maintain muscle mass and metabolism.
✔ Get enough sleep – Poor sleep increases obesity risk.
✔ Manage stress levels – Chronic stress can lead to emotional eating.
✔ Stay hydrated – Drinking more water helps control hunger and metabolism.
✔ Increased risk of heart disease, diabetes, high blood pressure, and joint issues.
✔ Malnutrition, weak immunity, and osteoporosis.
✔ Follow a balanced diet, exercise regularly, and make healthy lifestyle choices.
✔ Instant BMI classification and health risk assessment.
✔ Get NHS-approved recommendations for weight management.
