Energy in Human Diets

IB Topic A.2

Pages 220-229

How much energy is in nutrients?

Nutrient Typical energy per mass (KJ/100 g)

Carbohydrates 1760

Proteins 1720

Lipids 4000

So as you can see …

• Not all nutrients contain the same amount of energy

• Lipids contain more than twice the energy per 100g than the other nutrients

• Carbohydrates and proteins have relatively similar energy levels

• Why? • Bond between hydrogen and oxygen store energy

less efficiently • More of these bonds in carbs and proteins

• Lipids have a higher C-H bond ratio

In terms of a human diet …

• This is why it is possible to eats lots of fruits and veggies without worrying about too much energy (calorie) intake• Such foods are high in fiber – virtually no usable

energy

• When it comes to a balanced diet, it all depends on quantities

• Lipids contain more energy; consumed in smaller quantities

Sources of energy in different ethnic groups

• Food sources around the world are markedly different in different places

• Major crops include : • Rice• Wheat• Cassava• Maize • Fish and meat

Rice

• Most widely grown crop in the world • Main energy source for 1 in 5 people on Earth

• Type of grass native to southeast Asia and Africa

• Countries known for production: China, Japan, India, Indonesia, Thailand, and Vietnam

• Asian farmers produce 90% of the rice on Earth

• Rice is a complex carbohydrate

Wheat

• One of the first grains to be domesticated about 10,000 years ago

• Originated in the fertile crescent • Nile river delta to Mesopotamia

• Many cultures use wheat as energy source• Wheat flour bread, pasta, semolina (couscous),

cakes• Like rice, wheat is a carbohydrate• Major wheat consumers: Russia, Australia,

Turkey, Canada, and Iran

Cassava

• Shrub originated in South America • Today found in many tropical regions; Caribbean

• Tuber (root) • Source of starch

• Cooked and eaten like a potato, or made into flour (used in tapioca)

• Rich in carbohydrates, devoid of protein • Infants … protein deficiency …

Maize

• Corn (maize)• Starch• Originated in Central America • Today, Mexico is a leading producer

and consumer • Tortillas

Fish and meat

• Coastal and island populations rely on fish • Energy in fish is primarily protein, followed by fat;

no carbohydrates • The U.S. is the largest consumer of meat

• Average global consumption of meat per person per year is 37 kg

• In the U.S., it’s 90 kg • Most energy in meat comes from protein and

fat • Most nutrition experts warn Americans to eat less

meat and eat more high fiber, low fat foods

To sum it all up …

• See the table on page 222

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

• Excess carbohydrates leads to too much energy in the body • Complex carbs are broken down to simple

sugars which is used to make ATP• If the energy is not burned off, the excess

is stored• The sugar is converted into glycogen or fat• The body has limited storage of glycogen

• So if there is more glucose than glycogen, the rest is converted into body fat for storage

Excess fat in the diet

• Same idea as carbohydrates – the excess is stored

• But because fats contain twice the energy than carbs, the problem is intensified

• Also, are all fats equal? • Saturated vs. unsaturated

Excess protein in the diet

• An adult needs ~50 grams of protein/day• We have no way to store excess protein• Excess molecules get destroyed by the liver

and kidneys • Overworks these organs• Become hypertrophied (oversized)

• In the process of eliminating protein, or kidneys use calcium• If they cannot find enough, they leach it from bones• Consequences of high protein, low carb diets …

What about fiber?

• Another danger of excess carbs, proteins and fats is are you still going to be hungry to eat high fiber foods like fruits and vegetables?

Recap

• Appetite control system• Endocrine system• Digestive system • Nervous system

• BMI• Scale

Why are so many people obese?

• In 2002, the WHO estimated:• 300 million people worldwide are obese &

750 million are overweight

• In 2005, the WHO estimated: • The numbers rose to 400 million and 1.6

billion respectively

• Turn and talk: What might be causing the increase?

Some things to consider …

• A change in the types and quantities of food people eat

• Changes in physical activity • Farms vs. urban lifestyles • What about the spread of fast food

chains (like McDonalds overseas?)• Pressure/hours at work

Other factors to consider

• Family history/genetics• Your family and friend’s lifestyles• A type of adenovirus • Certain medications (such as

corticosteroids and antidepressants) • Medical problems (hypothyroid)

Anorexia nervosa

• Eating disorder• Anorexia – Greek for loss of appetite • Nervosa – nervous origin

• People believe they are overweight, but have a BMI that indicates they are normal or underweight

• Constant fear of gaining weight• Refuse to eat; regurgitate, over-exercise,

abuse laxatives • One thought of a young, white girls “disease”

• Now seen in all age groups, cultures, and men

Consequences of anorexia nervosa

• Endocrine system malfunctions• Hormones responsible for controlling such things

as menstrual cycle are not produced • Hair loss, dehydration, fainting, anemia, low

blood pressure, kidney stones or failure• Malnutrition immune system is weakened • Lack of calcium osteoporosis• Psychological and emotional problems

• Family, friends, romantic relationships • Treatments usually includes psychiatric help, not

just medical help

The most serious consequence is death

• Untreated anorexics literally starve themselves • 6%-20% of known cases

• Early diagnosis and treatment are important • Self image?

• Cultural pressure from media dictating what’s beautiful

• Traumatic experiences (a sense of control)• Physiological causes

• Genetic makeup• Depression, anxiety

Video Clip

• http://www.youtube.com/watch?feature=player_detailpage&v=VS2mfWDryPE