23: Nutrition

Question 1

Appreciate differences in the proportions of macronutrients in various diets.

Answer 1

Carbs, fats, & proteins are 3 classes of molecules that provide almost all the energy the body takes in, hence their designation as macronutrients.

In the 90’s there was a high carb low fat diet & it promoted obesity.

There are low carb high protein/ fat = atkins. Produces ketosis.

There are high complex carb, low refined carb etc.

Question 2

Appreciate the need to distinguish among carbohydrates: high- vs. low-glycemic index; high vs. low fructose content.

Answer 2

Recommendations for Carbs:

1.   Emphasize slowly metabolized carbos to reduce high insulin spikes & protect pancreas from overworking. The glycemic index is a measure of how quickly blood glucose levels (i.e., blood sugar) rise after eating a particular type of food.
2.   Reduce fructose consumption. Fructose consumption produces liver steatosis or fatty liver.

Question 3

Appreciate need to distinguish among fats: saturated, monounsaturated, polyunsaturated,
trans-fats, ω-3.

Answer 3

Trans fat is made from PUFA (polyunsaturated fatty acids). Trans fats are bad!

Consumption of saturated fat should be reduced also.

ω-3 FA’s: we should increase these in the diet, they decrease risk for heart disease.

Question 4

Understand why ketone bodies are elevated on a high-protein, high-fat, low-carbohydrate
diet.

Answer 4

In atkins you first use up all of your glycogen which has bound water, so you lose a lot of water weight first.

B oxidation produces ketone bodies.

Ketone body metabolism is efficient so peeing out ketones & breathing out acetone does not explain fat loss.

Perhaps ketosis has effects on beneficial feeding behavior. But its not clear why it works.

LDL cholesterol & TG decrease & HDL increases.

Long term studies must be done.

Question 5

Understand calculation and use of Resting Energy Expenditure (VERY TESTABLE)

Answer 5

Formulas for REE (kcal/day):

REE adult male = 900 kcal + 10w

(w = weight in kg)

REE adult female = 700 kcal + 7w

Use coefficients to calculate actual energy expenditure.

Activity coefficients for adjusted energy expenditure:
sedentary — 1.2
moderately active — 1.4
very active — 1.8

Question 6

Understand calculation and use of Body Mass Index (VERY TESTABLE)

Answer 6

BMI = kg/m2

Remember that BMI makes sense. It is a weight to height ratio so that higher weight has higher BMI.

< 18.5 = underweight

18. 5 - 24.9 = normal/ healthy
19. 0 - 29.9 = Grade 1 overweight = overweight
20. 0 - 39.9 = Grade 2 overweight = obese

≥ 40.0 = Grade 3 overweight = morbidly obese

Question 7

Understand calculation of weight loss

Answer 7

850 g • 9 kcal/g = 7650 kcal per kg of
adipose tissue lost.

so: 7650 kcal • #kg lose =

We may assume all weight loss is in
adipose tissue.

Adipose tissue is 85% fat, 15% water.
Therefore, 1 kg adipose tissue = 850 g
fat.

Equivalent calculations for weight gain.