Energy Balance and Weight Management

1. Energy Balance and Weight Management

2. Good health, including weight management, requires an equilibrium: Energy intake must equal energy output

3. Good health, including weight management, requires an equilibrium: If energy intake exceeds energy output (“positive energy balance”) the extra calories will be stored as fat - you will gain weight. Energy intake must equal energy output

4. Good health, including weight management, requires an equilibrium: If energy intake exceeds energy output (“positive energy balance”) the extra calories will be stored as fat - you will gain weight. If energy output exceeds energy intake (“negative energy balance”) your body will used stored fat and glycogen (and, if necessary, protein) to produce energy - you will lose weight Energy intake must equal energy output

5. Energy Balance: We’ve already discussed sources of energy intake:

6. Energy Balance: We’ve also discussed some types of energy output: Exercise: Cellular processes: Heat production:

7. Energy Balance: Intake is regulated by both internal and external cues: Internal cues: Your brain is constantly monitoring the energy needs of your body and whether or not these needs are being met. This has three components: Hunger - prompts eating Satiation - signals to stop eating Satiety - keeps you from starting to eat again

8. Energy Balance: Intake is regulated by both internal and external cues: External cues: Your brain creates a desire to eat a specific food or type of food, called appetite, which may or may not be directly related to meeting the energy needs of the body. Components: Mood Stress Social situations Time of day or Time of year

9. Energy Balance: Food intake These internal and external cues work together in a number of ways to influence food (and thus energy) intake: 1. Chewing, salivation, and swallowing send signals to the brain which decrease hunger and appetite

10. Energy Balance: Food intake These internal and external cues work together in a number of ways to influence food (and thus energy) intake: 1. Chewing, salivation, and swallowing send signals to the brain which decrease hunger and appetite 2. Stretching of the stomach (and possibly the intestine) sends signals to the brain which decrease hunger and appetite.

11. Energy Balance: Food intake These internal and external cues work together in a number of ways to influence food (and thus energy) intake: 1. Chewing, salivation, and swallowing send signals to the brain which decrease hunger and appetite 2. Stretching of the stomach (and possibly the intestine) sends signals to the brain which decrease hunger and appetite. 3. More than fifty different chemicals influence how the brain processes feelings of hunger, appetite, satiation, and satiety

12. Energy Balance: Food intake (Chemicals which influence how the brain processes feelings of hunger, appetite, satiation, and satiety) 3a. Neuropeptide Y is a protein produced in the brain which stimulates hunger and appetite and thus increases food intake

13. Energy Balance: Food intake (Chemicals which influence how the brain processes feelings of hunger, appetite, satiation, and satiety) (Neuropeptide Y) 3b. Ghrelin is a hormone produced in the stomach which stimulates hunger and appetite. It rises early in a meal, then falls quickly after the meal is over. It also slows down the body’s burning of fat.

14. Energy Balance: Food intake (Chemicals which influence how the brain processes feelings of hunger, appetite, satiation, and satiety) (Neuropeptide Y; Ghrelin) 3c. Leptin is a hormone produced by fat cells which stimulates satiety, thus decreasing food intake. It is produced in direct proportion to the amount of stored fat, but over time its production drops even of fat is unchanged.

15. Energy Balance: Food intake (Chemicals which influence how the brain processes feelings of hunger, appetite, satiation, and satiety) (Neuropeptide Y; Ghrelin; Leptin) 3d. Insulin is a hormone produced by the pancreatic islets which stimulates satiation and satiety, thus decreasing food intake.

16. Energy Balance: Food intake (Chemicals which influence how the brain processes feelings of hunger, appetite, satiation, and satiety) (Neuropeptide Y; Ghrelin; Leptin; Insulin) 3e. Cholecystokinin is a hormone produced by the small intestine which stiulates satiation and satiety, thus decreasing food intake

17. Energy Balance: Food intake These internal and external cues work together in a number of ways to influence food (and thus energy) intake: (1. Chewing, salivation, and swallowing) (2. Stretching of the stomach) (3. Chemicals) 4. The composition of your diet will also affect food intake: Proteins promote satiety the most Carbohydrates promote satiety moderately Lipids promote satiety the least Diets high in fiber promote satiety Solids promote satiety more than liquids

18. Energy Balance: Food intake These internal and external cues work together in a number of ways to influence food (and thus energy) intake: (1. Chewing, salivation, and swallowing) (2. Stretching of the stomach) (3. Chemicals) (4. Composition of the diet) 5. The flavor, texture, color, and temperature of food can influence appetite

19. Energy Balance: Food intake These internal and external cues work together in a number of ways to influence food (and thus energy) intake: (1. Chewing, salivation, and swallowing) (2. Stretching of the stomach) (3. Chemicals) (4. Composition of the diet) (5. Flavor, texture, color, temperature) 6. The smell of food has a strong effect (either positive or negative) on hunger and appetite

20. Energy Balance: Food intake Many cultural & societal factors also influence food intake: + Your mom or your coach: “Eat, Eat!” Social situations with lots of people Large serving sizes Advertising Dim lighting/romance Distraction from loneliness, anger, boredom - Awareness of what you are eating Fear of gaining weight (anorexia)

21. Energy Balance: Food intake Obviously, the “cues” which stimulate or inhibit hunger, appetite, satiation, and/or satiety are very complex and they all interact in multiple ways. Nutritionists often talk about this as “contol by committee” – no single factor can be identified, but working together these factors effectively stimulate or inhibit a) The need to eat (hunger) b) The desire to eat (appetite) c) The feeling of “I’m full so I’ll stop now” (satiation) d) The feeling of “It’s not time to eat again yet” (satiety)

22. The other side of the energy balance equilibrium, of course, is Energy Output. Just as there are many ways you gain energy through food intake, there are many ways you use energy. Your textbook lists three components of energy expenditure but Physiologists consider heat production to be separate from other types of “resting” energy expenditures

23. Energy Balance: Energy Output 1. Ingesting, digesting, absorbing, and metabolizing the food you eat requires a significant amount of energy. This is called the Thermic Effect of Food. At rest, this is 5% to 10% of total expenditure. It peaks one or two hours after eating and lasts for four to five hours.

24. Energy Balance: Energy Output 2. By far, the largest energy expenditure is the Resting Energy Expenditure (REE) needed for the basic body functions to stay alive such as breathing, circulating blood, nerve function, moving molecules into and out of cells, maintaining body temperature, bone and muscle growth, forming urine, fighting infections, reproducing, etc. At rest, this is 60% to 75% of total energy. It is also known as the Basal Metabolic Rate (BMR)

25. Energy Balance: Energy Output Resting Energy Expenditure or Basal Metabolic Rate are defined as the amount of energy (kcals) used for these functions over a full day. When calculated per hour it is the Resting Metabolic Rate (RMR).

26. Energy Balance: Energy Output Resting Energy Expenditure or Basal Metabolic Rate are defined as the amount of energy (kcals) used for these functions over a full day. When calculated per hour it is the Resting Metabolic Rate (RMR). Thus, if you maintained a Resting Metabolic Rate of 60 kcal/hour then your Resting Energy Expenditure would be (60 kcal/hour) x (24 hours) = 1,440 kcal/day

27. Energy Balance: Energy Output Resting Energy Expenditure primarily depends on the lean body mass – the total mass of everything that isn’t fat. Thus, a muscular person will have a higher RMR and REE than a nonmuscular person.

28. Energy Balance: Energy Output Resting Energy Expenditure primarily depends on the lean body mass – the total mass of everything that isn’t fat. Thus, a muscular person will have a higher RMR and REE than a nonmuscular person. In general, men have more lean body mass than women, but in both sexes the lean body mass (and thus both RMR and REE) decline with age.

29. Energy Balance: Energy Output Resting Metabolic Rate can be estimated by multiplying the weight in kilograms by 1 kcal/kg for men and 0.9 kcal/kg for women and Resting Energy Expenditure can then be calculated by multiplying this by 24 hours.

30. Energy Balance: Energy Output However: many other factors can change resting metabolic rate and resting energy expenditure.

31. Energy Balance: Energy Output 3. The most variable energy expenditure is the Energy Expenditure of Physical Activity. For most people, this is 15% to 30% of total expenditure, but for extremely active people it can be as much as 50% or 60% of total expenditure.

32. Energy Balance: Energy Output 3. The most variable energy expenditure is the Energy Expenditure of Physical Activity. Muscle contraction, whether it is used to walk around during a normal schoolday, climb up Sugarloaf, or run the Twin Cities Marathon, requires a very large amount of energy.

33. Energy Balance: Energy Output Energy Expenditure of Physical Activity: For example: An 80 kg (175 pound) person uses approximately: 95 kcal per hour when sleeping 140 kcal per hour when reading or studying 275 kcal per hour when walking at a moderate pace 550 kcal per hour when jogging 650 kcal per hour when swimming laps 1,300 kcal per hour when running at top speed

34. Energy Balance: Energy Output

35. Energy Balance: Energy Output While it can be useful to separately determine the Thermic Effect of Food, the Resting Energy Expenditure, and the Energy Expenditure of Physical Activity, most often it is more important to know the sum of all three, the Total Energy Expenditure (TEE)

36. Energy Balance: Remember: The total amount of energy your body expends each day must equal the number of calories consumed in food, so you can calculate an Estimated Energy Requirement – the amount of energy intake needed each day to maintain energy balance in a healthy individual of normal weight. Total Energy Expenditure Estimated Energy Requirements. =

37. Energy Balance: Energy Intake but there are many online calculators into which you can enter these values and determine your EER. For most people, this is between 2,000 and 2,800 kcal/day

38. Body Composition: Note that both your Estimated Energy Requirements (calories consumed) and your Estimated Energy Expenditure (calories used) are strongly influenced by your body weight.

39. Body Composition: Note that both your Estimated Energy Requirements (calories consumed) and your Estimated Energy Expenditure (calories used) are strongly influenced by your body weight. However: not all “weight” is equal. Muscles, bones, blood, and solid organs are relatively heavy

40. Body Composition: Note that both your Estimated Energy Requirements (calories consumed) and your Estimated Energy Expenditure (calories used) are strongly influenced by your body weight. However: not all “weight” is equal. Muscles, bones, blood, and solid organs are relatively heavy Fat and other connective tissues are relatively light

41. Body Composition: The commonly accepted method for assessing your body composition is the Body Mass Index (BMI) which is the ratio of your weight to the square of your height. BMI = or x 704.5 This correlates well with the amount of lean mass and fat you have, and with your risks for developing a number of diseases. weight (kg)weight (lbs) height (m2) height (in2)

42. Body Composition: Normal: BMI between 18.5 and 24.9

43. Body Composition: Underweight: BMI below 18.5 Normal: BMI between 18.5 and 24.9

44. Body Composition: Underweight: BMI below 18.5 Normal: BMI between 18.5 and 24.9 Overweight: BMI between 25 and 29.9

45. Body Composition: Underweight: BMI below 18.5 Normal: BMI between 18.5 and 24.9 Overweight: BMI between 25 and 29.9 Obese: BMI above 30

46. Body Composition: Excess body fat, measured as a high Body Mass Index, is a well established indicator of increased risk for diseases such as diabetes, stroke, heart disease, and many cancers.

47. Body Composition: Excess body fat, measured as a high Body Mass Index, is a well established indicator of increased risk for diseases such as diabetes, stroke, heart disease, and many cancers. However, BMI is just an estimate for most adults: it’s less accurate for predicting risk in children, the elderly, highly muscular individuals, and well-trained athletes. In some instances, therefore, more direct measurements of the amount of fat are necessary.

48. Body Composition: (More direct measurements of fat are often necessary) The most accurate way to measure fat is a technique called “dual energy X-ray absorptiometry”. As its name implies, this requires a specific instrument which is not available outside of a hospital setting and is very expensive.

49. Body Composition: (More direct measurements of fat are often necessary) Less expensive methods include Underwater or hydrostatic weighing Air displacement in a contained space Both take advantage of the fact that fat is much less dense than bone, muscle, etc. so it displaces less water or air per kilogram or per pound.

50. Body Composition: (More direct measurements of fat are often necessary) Less expensive methods include Bioelectrical impedence, which takes advantage of the fact that fat conducts electricity much more slowly than other tissues