A healthy diet satisfies three needs
• Fuel to power the body
• Organic molecules to build molecules
  
• Essential nutrients—raw materials that animals cannot make for
themselves
Chemical energy powers the body
Nutrients are oxidized inside cells to make ATP

• Proteins, carbohydrates, and fats are the main sources of calories

• Basal metabolic rate (BMR): energy a resting animal requires each day

• Metabolic rate: BMR + the energy needed for physical activity

• Excess energy is stored as glycogen or fat

An animal’s diet must supply essential nutrients
• Essential nutrients cannot be made from any raw material

• Undernourishment—not enough calories

• Malnourishment—missing essential nutrients

• Animals cannot produce eight of the 20 amino acids named essential amino acids.
• These eight amino acids must come from the diet.

A healthy diet includes 13 vitamins and many essential minerals
.

• Essential vitamins and minerals           
– Required in minute amounts  -
– Extreme excesses can be dangerous    -
– Excess water-soluble vitamins can be eliminated in urine
–
– Excess fat-soluble vitamins accumulate to dangerous levels in body fat
–
– Minerals are simple inorganic nutrients usually required in small amounts

– Calcium and phosphorus are required in larger amounts

CONNECTION: Diet can influence cardiovascular disease and cancer

• A healthy diet may reduce the risk of cardiovascular disease and cancer

• Two main types of cholesterol :
– LDL : contributes to blocked blood vessels and higher blood pressure

– HDL : tends to reduce blocked blood vessels
• Exercise increases HDL levels

• Smoking decreases HDL levels