A.2 Energy in human diets

How much energy is in nutrients?

CARBOHYDRATES	1,760kJ/100g
PROTEINS	1,720kJ/100g
FATS	4,000kJ/100g

Sources of energy in different ethnic groups

ETHNIC GROUP	MAIN SOURCES OF ENERGY
Asian	Rice
Pacific Islanders	Cassava
African Groups	Cassava
European	Wheat/ Potatoes
Euro-American	Wheat/ Potatoes
Native American	Corn/ Maize
Andean	Potatoes/ Rice

Health consequences of diets rich in carbohydrates, fats, and proteins

-    Excess carbohydrate in the diet

-    eating excessive amounts of carbohydrates results in too much energy entering the body

-    Complex carbohydrates are broken down into simple sugars which can be used to make ATP for muscles and other tissues. If the energy from the sugars is not burned off by physical activity, the excess is stored.

-    Excess fat in the diet

-    Eating excess fat in the diet has some similar consequences to eating excess carbohydrates.

-    But fats contain over twice as much energy per unit mass than carbohydrates, so the problem of storing excess energy is intensified.

-    Excess protein in the diet

-    Increasing in blood pressure, atherosclerosis and the incidence of coronary heart disease

-    Atheromas develop in the arteries and significantly reduce the diameter of the artery wall needed for pulse flow

-    This may lead to the formation of clots in the artery, and if this occurs in the coronary arteries it may lead to a heart attack

Appetite control system

-    Appetite is the desire to eat

-    Hypothalamus plays an important role in regulating appetite.

-    If your stomach fills with food, expands and stimulates nerve cell of the vagus nerve. A signal is sent to the hypothalamus to stop eating. The intestines produce various hormones to send signals about hunger and satiety to the brain.

Body mass index (BMI)

-    The scientific answer to decide to be whether or not an individual has an appropriate mass is to calculate the body mass index(BMI)

-    BMI=(mass in kg)/(height in m)^2

Underweight, normal or overweight?

BMI	Status
below 18.5	underweight
18.5-24.9	normal weight
25.0-29.9	oveweight
30.0 and above	obese

-    The BMI can be used as a guide but it should not be used as the indicator to decide if you are at a healthy body mass.

Why are so many people obese?

-    These days, the number of obese people are continue to increase.

-    a change in the types and quantities of food people eat

-    changes in the amount of physical activity people do on a daily basis

-    agriculture life to urban life

Anorexia nervosa

-    eating disorder in which people have the firm conviction that they are overweight whatever they are normal or underweight

-    fear of gaining body mass

-    strong obsession that they are overweight

Consequences of anorexia nervosa

-    endocrine system malfunctions=>hormones responsible for controlling such things as the menstrual cycle are not produced and distributed in the body

-    stop menstruating

-    loss of head hair, dehydration, fainting, anaemia, low blood pressure, kidney stones or kidney failure

-    skin turn yellow, fine hair can grow all over the body

-    lack of calcium

-    osteoporosis

-    psychological and emotional problems

-    affecting family relationships, friendships and romantic relationships

-    untreated and literally starve themselves to death

-    6 to 20%