A person is considered “underweight” when has a Body Mass Index below 18.5. Underweight, such as obesity, it indicates that the body is in a no-healthy situation.
The body, if properly fed and healthy, tends to remain in the normal weight parameters (BMI 18.5 to 25). You can go underweight only when you are not eating enough or if you have a disease that does not allow adequate food or interferes with the absorption of nutrients. People who are underweight, especially severe, are more at risk of diseases due to malnutrition or lack of certain nutrients and the risk of death increases dramatically with the fall of the IMC.
What is meant by “normal weight”?
People are considered “normal weight” when they have a Body Mass Index (BMI) between 18.5 and 25.
This indicates that they have a proper weight to height, which is basically in good nutritional health.
But be careful! This can not be true if you have diseases that involve or if you suffer from a disorder food.
Always remember: the weight (and therefore the IMC) can’t give us complete information about our state of nutritional health!
What is meant by “overweight”?
People are considered “overweight” when they have a Body Mass Index between 25 and 30, in particular when it is proved that the IMC is due to an excess of Body Fat. It may happen that an athlete have a BMI above 25, but because very muscular: in this case we are not talking of overweight. Overweight people with a good nutritional balance are not running severe risk for the health, but must pay attention to lifestyle because they have greater risk of developing obesity, much more serious condition as it is correlated with many chronic diseases.
What is meant by “obesity”?
It is said that a person suffers from obesity when has a Body Mass Index greater than 30, and just like to define “overweight,” it should be noted that the IMC has to be due to an excess of Body Fat to talk about obesity. Obesity is a disease which is alarming the West, because the excess body fat increases dramatically the risk of developing chronic cardiovascular diseases (such as hypertension, atherosclerosis, heart attack) and metabolic (diabetes), and then falls the quality of life of people who suffer from it.
It was proved that obesity has genetic basis, but these represent only a predisposition. It means that a person does not develop excess body fat just because it is genetically predisposed, but also because has a wrong lifestyle (overeating and sedentary lifestyle). Then people who are genetically predisposed to obesity can avoid its developing simply adopting an healthy lifestyle. Conversely, people who are not predisposed, they can become obese if they exceed in food and have a sedentary lifestyle.
This is why nutrition and physical activity are the two cornerstones in the treatment of obesity, or rather in the prevention!
WHO-World Health Organization- Department of Nutrition for Health and Development (NHD) (http://www.who.int/topics/nutrition/en/)