Nutrition Science and Obesity

Study Notes

Normal, healthy men have a body fat percentage of 15-20%, while normal, healthy women have a percentage of approximately 25-30%.
Obesity is the most common nutritional disorder worldwide and directly or indirectly accounts for a significant portion of health-related expenses.

The first phase of nutrition science involved discovering, characterizing, and synthesizing essential nutrients and describing their deficiency syndromes in detail.
The second phase involved accumulating evidence on the relationships of diet and nutritional status to chronic diseases, such as coronary heart disease (CHD), cancer, diabetes, and other leading causes of death.

Of the seven major risk factors for CHD, four are related to diet: hypercholesterolemia, hypertension, obesity, and diabetes.
Colorectal cancer is the third leading cause of cancer mortality in men and women, and its risk correlates positively with the intake of red and processed meats, obesity, and alcohol.
Obesity increases the risk of liver cancer, with alcohol being the strongest risk factor.
Type 2 diabetes mellitus is strongly associated with obesity, especially abdominal obesity, so maintaining a desirable body weight throughout life is crucial in preventing and treating type 2 diabetes.

The body mass index (BMI), also known as the Quetelet index, is commonly used to define obesity, and it correlates closely with the degree of body fat in most settings.
BMI is calculated as weight (in kilograms) divided by height squared (in meters), with a modified formula for pounds and inches: BMI= Weight (IB) / Height (inches) 2 X 703.
However, BMI has limitations, such as overestimating body fat in muscular individuals and underestimating it in elderly individuals and those with sarcopenia.
Alternative indices for estimating obesity include skinfold thickness measurements and anthropometric measures, such as waist and hip circumferences.

For men, a percentage of body fat greater than 25% defines obesity, with 21-25% being borderline.
For women, over 33% defines obesity, with 31-33% being borderline.