Nutritional Factors

1. Nutritional Factors Influencing Body Composition

2. Overconsumption • The government recommends 1600 calories a day for the average sedentary woman and 2200 for men. • In 2000, our reported per capita daily caloric consumption was 1877 for women and 2618 for men.

3. Nutrition and Exercise Where do we get the energy for movement? What should we eat to insure optimal health and fitness?

4. Nutrition and Exercise • Energy for movement comes from the food we eat. • The three sources of energy are: • Carbohydrates • Fats • Proteins

5. Nutrition and Exercise General Recommendations: • CHO 55-65% • CNS • Primary fuel source • Only anaerobic fuel source • Required for fat metabolism • Required for protein metabolism

6. Nutrition and Exercise • Fat 20-30% • Major fuel source for endurance activity • Essential component of cell membranes and nerve fibers • Insulation • Shock absorption • Hormone production • Fat soluble vitamins

7. Nutrition and Exercise • Fat • High in kcal per weight • Low fat = <20% • Read labels - for something to be low fat, there should be no more than 1 gram of fat for every 50 kcals. • 100 kcals : 2 g fat = 18% fat (9 kcals per gram of fat)

8. Nutrition and Exercise • Protein 10-15% • Growth and maintenance of lean tissue • Repair of damaged tissue • Fuel source during starvation

9. Old Food Guide Pyramid

10. Food Guide Pyramid • Key Points (2004): • At least 3 one-ounce servings of whole grains each day (instead of refined sugars and white bread) • Whole grains contain more fiber which has been shown to reduce the risk of heart disease and diabetes • Increase daily intake of fruits and vegetables, whole grains, and nonfat or low fat milk and milk products

11. Food Guide Pyramid www.mypyramid.gov

12. Nutrients • CHO • Fat • Protein • Water • Vitamins • Minerals

13. Vitamins • Fat Soluble • A D E K • Water Soluble • B Complex • C

14. Free Radicals and Antioxidants • Free-radical generation increases after acute exercise and potentially causes oxidative tissue damage. • May lead to cancer. • Consuming antioxidants (e.g., vitamin E and β-carotene) can trap free radicals and prevent this action.

15. Minerals • Calcium • Phosphorus • Magnesium • Iron • Potassium • Sodium

16. Calcium • RDA for most adults = 1000 mg • For teenagers = 1300 mg • For those over 50 = 1200 mg • Highest food sources are dairy and calcium-fortified orange juice.

17. Iron • RDA = 8 mg for men and postmenopausal women • 18 mg for pre-menopausal women • 27 mg for pregnant women • Upper limit = 45 mg or stomach upset can occur.

18. Zinc • RDA = 11 mg for men, 8 for women • Upper limit = 40 mg • More can block absorption of another vital nutrient, copper.

19. Water • Important before, during, and after physical activity. • 2.5 liters per day. • Major factor limiting exercise performance. • Thirst.

20. Dieting • Starvation diets will cause weight loss. • However, they also cause physiologic dysfunction and potentially death. • In addition to fat loss, you lose muscle mass, bone mass, and water volume.

21. Yo-Yo Dieting • The more you diet, the fatter you become. • When you lose, you lose muscle, fat, water, and bone. • When you return to your normal lifestyle, you add on fat and water, but unless you increase activity levels drastically, you don’t add bone or muscle mass.

22. Fad Diets • Why are they so popular? • They give the false impression that you can eat what you like, in the quantities that you want, without having to exercise, and still lose weight. • Very seductive message.

23. Low Carb • Hype: • Carbs are not healthy • Carbs negatively impact blood sugar levels through high glycemic index raising insulin levels • Low blood sugar leads to hunger • Invented concept of “Net Carbs”

24. Low Carb • Facts: • Low blood sugar hasn't been directly linked to hunger. • Unless you have diabetes, blood sugar remains generally stable anyway. • When you stop eating carbohydrates, your brain stops regulating serotonin, a chemical that elevates mood and suppresses appetite.

25. Low Carb • Facts: • Only carbohydrate consumption naturally stimulates production of serotonin. • When serotonin is made and becomes active in your brain, its effect on your appetite is to make you feel full before your stomach is stuffed and stretched. • The brain makes serotonin only after a person consumes sweet or starchy carbohydrates.

26. Low Carb • Facts: • The kicker is that these carbohydrates must be eaten in combination with very little or no protein. • This can explain why people may still feel hungry even after they have eaten a 20-ounce steak. • Their stomachs are full but their brains may not be making enough serotonin to shut off their appetites.

27. Low Carb • August 1st, 2005 Atkins Nutritionals declares bankruptcy

28. Body Composition Questions • Why do low-carbohydrate diets produce such a rapid weight loss? • Diets that limit or totally exclude CHO produce a rapid weight loss. • When CHO intake is low, muscle glycogen stores are depleted rapidly.

29. Body Composition Questions • For every gram of CHO, 3 grams of H20 are stored in the body. • When glycogen stores are depleted, the loss of water leads to a dramatic weight loss because each liter of water weighs approximately 2 lbs.

30. Body Composition Questions • The weight is regained rapidly, however, when CHO intake returns to normal.

31. Protein Power • 850-1,100 kcal/d • High protein

32. The Zone • 1,300 kcal/d for women and 1,700 kcal/d for men • Follow the 40-30-30 rule • No foods are off limits, but they claim some foods are better than others • Example – broccoli, celery, and grapes = good • Cereal, bagels, and bananas = bad • No real justification for these classifications

33. Sugar Busters! • 1,200 kcal/d with 28% of total energy intake from fat • 33% of total energy intake from protein

34. South Beach Diet • Steer clear of bread and beer (maltose) • No fruit, bread, sugary snacks, potatoes, pasta, or rice • No scientific support for these recommendations, but at least allows whole grains, some fruit (later), and cuts back on saturated fat

35. Nutrition Questions • Why are low carbohydrate diets unsafe? • Low CHO intake may lead to fatigue, hypoglycemia, and ketosis.

36. Nutrition Questions • Low carb diets are detrimental to anaerobic work capacity because of reduced muscle glycogen stores and decreased rate of glycolysis.

37. Nutrition Questions • Many of the fad diets (Atkins Diet Revolution, Sugar busters, the Zone) result in weight reduction primarily because they are low calorie diets.

38. Nutrition Questions • Low carb diets are high in fat, saturated fat, and cholesterol.

39. Nutrition Questions • The nature of low carb diets is a diet low in fruits, vegetables, grains, and beans. • These foods are all high in health promoting and disease preventing properties.

40. Nutrition and Exercise • Do we need to consume large amounts of protein if we exercise and wish to increase muscle mass?

41. Nutrition and Exercise Recommended Levels of Protein Consumption RDA Sedentary Endurance Strength g/kg/day 0.8 1.2 - 1.4 1.4 - 2.0

42. Nutrition and Exercise • “No valid evidence exists supporting the notion that protein intake exceeding 1.8 - 2.0 will provide additional advantage” • International Journal of Sports Nutrition

43. Nutrition and Exercise • “The recommended levels may be reached within the total protein percentage recommendations of 10-15% of all calories consumed daily” • International Journal of Sports Nutrition

44. Nutrition and Exercise • Example • 220 lbs male = 100 kg • excessive intake = 2.0 (g/kg/day) • daily need = 200 grams • typical consumption = 6000 kcals 10-15% of 6000 kcal = 600 -900 kcal of protein • divided by 4 kcals per gram • 150-250 grams of protein.

45. Amino Acids and Protein • In all but a few exceptional cases, the maximal contribution of protein as an energy source during exercise ranges between 2% and 10% of the total energy expended. • (Gibala; Hargreaves, and Tipton, 2000)

46. Amino Acids and Protein • In theory, amino acids could contribute to carbohydrate metabolism during exercise, but there is no hard evidence that this occurs or has any bearing on sport performance. • (Gibala; Hargreaves, and Tipton, 2000)

47. Amino Acids and Protein • Supplementation of the athlete’s diet with branched-chain amino acids apparently does not benefit exercise performance. • (Gibala; Hargreaves, and Tipton, 2000)

48. Amino Acids and Protein • The most important factors for optimizing growth when one performs resistance exercise are: • Adequate resistance • Adequate caloric consumption, including just after lifting • Plenty of rest between sessions • (Gibala; Hargreaves, and Tipton, 2000)

49. Amino Acids and Protein • With rare exceptions athletes require 1.2 – 1.6 grams of protein per kg day. • This amount of protein can almost always be obtained in the normal diet. • (Gibala; Hargreaves, and Tipton, 2000)

50. Amino Acids and Protein • There is no solid evidence that special mixtures of amino acids provide any advantage over normal dietary proteins in stimulating muscle growth. • (Gibala; Hargreaves, and Tipton, 2000)