Lifestyle factors change the risk of non-communicable diseases. Obesity develops when a person takes in more energy from food than their body uses, so the extra is stored as fat. Malnutrition means a diet that is not balanced. It can mean too little of a nutrient, which leads to deficiency diseases, or too much energy, which leads to obesity. Regular exercise and a balanced diet help to prevent obesity.
Body mass index (BMI) is mass (kg) ÷ height (m)2, that is, mass divided by height squared. For example, a person of 64 kg and 1.60 m has a height squared of 2.56, so BMI = 64 ÷ 2.56 = 25. A BMI of 18.5 to 24.9 is healthy, 25 to 29.9 is overweight and 30 or more is obese. The waist : hip ratio is the waist measurement divided by the hip measurement. A higher ratio means more fat stored around the abdomen, which carries a greater risk of cardiovascular disease and type 2 diabetes.
Heavy drinking of alcohol over many years damages the liver. It can cause a fatty liver, cirrhosis (scarring) and liver cancer. Smoking harms the cardiovascular system: carbon monoxide reduces the oxygen carried by the blood, and chemicals in the smoke damage artery walls and raise blood pressure, so fatty deposits build up and the arteries narrow.
The effects show at different levels. Locally, a town with few places to exercise and many fast food outlets may have more obesity. Nationally, these diseases cost the health service money and cause lost working days. Globally, obesity and cardiovascular disease are becoming more common in many countries, while malnutrition from too little food is still more common in poorer countries.