Energy Balance and Body Composition

1. Energy Balance and Body Composition • We expend energy continuously and eat to refuel. Ideally, our energy intake from food we consume covers energy expenditures without having too much excess energy left over to store in our body as fat. • Stored fat is used for energy between meals. The amount of body fat a person deposits in, or withdraws from our adipose tissue depends on the energy expended during the day. “Lecture 7: Energy Balance and Body Composition PowerPoint" by Dr. Michael Kobre, Achieving the Dream OER Degree Initiative, Tompkins Cortland Community College is licensed under CC BY 4.0

2. Energy Balance • Most of us maintain a steady energy balance over time. On any given day, we may eat a little more or a little less than usual, and our weight may go up or down a pound or two, but, for the most part, we stay in energy balance. When balance shifts, our weight changes. For each 3500 Kcals eaten in excess of body needs, a pound of body fat is stored.

3. Energy Balance • If we are trying to lose weight, we should keep in mind that gradual weight loses are more likely to be maintained than rapid losses. If our food energy is restricted too severely, we will lose lean tissue and may not receive enough needed nutrients. Also, restrictive eating may set in motion the unhealthy cycle of repeated dieting and binge eating.

4. Energy Balance • In the body, quick changes in weight are not just changes in fat. Weight gained or lost rapidly includes some fat, large amounts of fluid, and also some lean tissues such as muscle and bone minerals as well. Even over the long term, the composition of weight gained or lost is normally about 75% body fat and 25% lean tissue. During extreme dietary restriction or starvation, losses of fat and lean tissue are about equal.

5. Energy in Foods • The energy values of foods we consume can be computed easily from the amounts of carbohydrate, fat, and protein in foods… Keep in mind that fat’s energy value is 9 Kcal/gram, Carbohydrate and Protein contains approximately 4 Kilocalores of energy per gram.

6. Food Intake • To achieve energy balance, our body must meet its requirements without taking in too much or too little energy from foods. Somehow our body alerts us of how much and how often we should eat, when to start eating, and when to stop. There are many internal signals in the body that initiate or delay the process of refueling.

7. Hunger • Is the physiological drive for food that initiates our food seeking behavior. Hunger is a physiological response for food that is triggered by chemical messenger molecules that originate and act on the brain, primarily in the area called the hypothalamus. Our hunger can be influenced by many things, nutrients in the bloodstream or the size and composition of a preceding meal. Environmental temperature along with many other conditions influence eating too.

8. Hunger • Our body’s hunger response can adapt to accommodate changes in food intake. Receptors in the GI tract adapt and change their responses to diet depending on our nutrient intake. If a person changes his diet to a high-fat intake, after a few weeks, the GI tract will make adjustments to handle increased fat intake more efficiently.

9. Appetite • Hunger is only one of the signals determining whether a person will eat. Our appetite also ca initiate eating. A person may experience appetite with out needing to eat, for example, when a presented with a fresh piece cake, even though they are stuffed from consuming a recent large meal. In contrast, a person may be starved but when faced with unfamiliar foods, stress, or an underlying illness, consuming anything becomes a chore for them.

10. Satiation • During the course of a meal, as food is eaten, the GI tract fills, hunger diminishes and satiation develops. Receptors in the stomach respond to stretch, signals are sent to the brain and the person begins to feels too uncomfortable to keep eating. Nutrients also trigger the release of GI hormones. Both gastric distention, and hormones send messages to the hypothalamus region. The response triggers satiety and people stop consuming food.

11. Satiety • For a period of time after a meal, the feeling of satiety continues to suppress hunger and allows the person to feel full and satisfied. • Satiation thus informs us of when to stop eating, satiety maintains the feeling of not starting to eating again for a while.

12. Overriding Hunger and Satiety Signals • It is not surprising that eating can be triggered by signals other than hunger. • Some people experience food cravings when the body does not refueling. Some people experience food cravings when they are bored or depressed, or anxious. Some people eat in response to stress.

13. Overriding Hunger and Satiety Signals • Eating can also be suppressed by signals other than satiety, even if a person is very hungry. The eating disorder anorexia nervosa, can cause tremendous restraint in folks to ignore hunger pangs for fear of gaining weight. • Studies have shown that around half of people cannot eat during times of stress.

14. Overriding Hunger and Satiety Signals • Why some of us overeat in response to stress and others cannot eat at all remains a bit of a mystery. Some of the factors that appear to be involved include how the person perceives the stress, early socialization to eating practices and whether our usual eating behaviors are restrained or enhanced during stressful times.

15. Nutrients, Satiation, and Satiety • A major factor in which foods produce satiation and sustain satiety depends greatly on the nutrient composition of a meal. • Research has shown that of the 3 energy-yielding nutrients, protein has the most satiating affect on hunger. Foods that are rich in complex carbohydrates and fibers (not simple sugar!) can also extend the duration of satiety by filling our stomach and helping to delay intestinal motility making us feel full faster.

16. Nutrients, Satiation, and Satiety • Fat, o the other hand has a weak satiating effect. Consuming meals high in fat content leads to passive over consumption. Fatty foods offer enhanced flavor, which entices people to eat more, and contain more energy density, which delivers more Kilocarlores per mouthful, and produces less satiation during a meal with much less satiety after a meal.

17. Nutrients, Satiation, and Satiety • If we compare high fat foods to whole foods high in fiber such as whole-grain pastas, oatmeal, fish and lean beef are highly satiating-and they provide a rich array of nutrients with less energy per gram too.

18. Message Central-The Hypothalamus • As we have said, eating is a complex behavior that is controlled by a variety of psychological, social, metabolic, and physiological factors. • In the brain, the hypothalamus appears to be the control center, it’s function relating to nutrition is integrating info concerning energy intake, expenditure, and energy storage from all parts of the body.

19. Message Central-The Hypothalamus • We have several chemicals in our brain that participate in the appetite control and energy balance. By studying the actions of these molecules, researchers hope to one day be able to help control appetite in people who have eating control issues.

20. Message Central-The Hypothalamus • One of the chemicals related to nutrition is a molecule named neuropeptide-Y. this molecule causes us to have carbohydrate cravings and initiates our eating response. It also decreases energy expenditure, and increases our fat storage, all, factors that favor positive energy balance and weight gain.

21. Energy Out: The Kcals the Body Spends • During energy Metabolism, heat is released whenever our body breaks down carbohydrates, fats, or proteins for energy and again when we use energy to perform functions. The body’s generation of heat is known as thermo genesis. In a lab setting, the release of heat can be measured to determine the amount of energy a person has expended.

22. Energy Out: The Kcals the Body Spends • The total amount of energy our body spends reflects three main categories of thermo genesis: • Basal thermo genesis (basal metabolic rate) • Exercise-induced thermo genesis (physical activity producing extra heat) • Diet-induced thermo genesis (the heat produced when processing food in the body). • A 4th category is sometimes involved: Adaptive thermo genesis.

23. Energy Out: The Kcals the Body Spends • Basal Metabolism: the energy needed to maintain life when our body is at complete digestive, physical, and emotional rest. • Basal Metabolic rate, BMR: the rate of energy use for metabolism under specified conditions: after a 12 hour fast and restful sleep, without any physical activity or emotional excitement, and in a comfortable environmental setting. It is usually expressed as Kcal/Kg body wt/hour.

24. Energy Out: The Kcals the Body Spends • Lean Body Mass Makes a Difference! One way we can increase BMR is to exercise regularly to maximize lean body mass and reduce body fat composition. BMR will decline during adulthood as lean body mass diminishes. This change in body composition occurs, in part because some of the hormones that influence metabolism become more or less active as a person ages and we usually are less active as we age.

25. Energy Out: The Kcals the Body Spends • Keep moving to stay lean! Keep walking, lifting, climbing, and participating in other physical activities as you age. • Voluntary physical activities tend to decline with age bringing about an average reduction in energy expenditure to ~5% per decade of life

26. Energy Out: The Kcals the Body Spends • Physical Activity: is a major component of a person’s energy output. During physical activity, the muscles need extra energy to function. Our heart and lungs need extra energy to deliver nutrients and oxygen and dispose of wastes during times of increase physical activity.

27. Energy Out: The Kcals the Body Spends • How much energy is needed for any activity, whether playing tennis or reading a book depends on three main factors: muscle mass, body weight, and the body part being moved. The larger the muscle and the heavier the weight of the body part being moved, the more energy is required and used moving the body part(s).

28. Adaptive Thermogenesis • Occasionally additional energy must be spent when a person has to adapt to changed internal or external circumstances. When our body is adapting to physical conditioning, during extreme cold exposure, overfeeding, starvation, and trauma, energy demands increase. Often, these conditions require building extra tissues, producing more enzymes and hormones required to cope with the increased metabolic demands.

29. Adaptive Thermogenesis • In many cases these increased energy requirements can make a considerable difference in the total energy our body spends. Because this component of energy expenditure is so variable and specific to individuals and conditions, it is not included when calculating normal energy requirements in a healthy state.

30. How We Estimate Energy Requirements • When calculating energy requirements, for our body, the following components of energy expenditure need to be considered: • Energy we spend on BMR • Energy we spend on physical activities

31. Body Weight, Body Composition, and Health • Because direct measurement of body composition is impossible in living human beings (we can’t separate tissue out of the body and live), researchers have to measure body composition using indirect methods that are less accurate.

32. Body Weight, Body Composition, and Health • Body composition is based on the following assumption: • Body weight equals fat + lean tissue (including body water). • Keep in mind weight gained and lost tells us nothing about how our body’s composition may have changed. Often, weight is the measure most people use to judge their level of fatness and this is far from accurate.

33. Body Weight, Body Composition, and Health • For many of us, being overweight means being over fat, but this is not necessarily the case. Athletes with dense bones and well-developed muscle may be over-weight by some standards, but actually have very little body fat. Conversely, inactive people may seem to have acceptable weights, when, in fact they may have too much body fat and not enough lean tissue to function well.

34. Defining Healthy Body Weight • How much should we weigh? How can we know if our weight is appropriate for our height? How can we know if our weight is negatively effecting our health? Although these questions may seem easy to answer, sometimes the experts can’t even agree on the answers.

35. How Do We Define Healthy Weight? • Health experts often try to identify body weights associated with good health and longevity of life. Healthy body weight is defined by three main criteria: • Having a weight within the suggested range for body height. • Having a fat distribution pattern in the body that is associated with a low risk of illness and premature death. • Having a medical history that demonstrates an absence of risk factors associated with obesity. e.g. elevated levels of blood cholesterol, blood glucose, or blood pressure.

36. Defining Healthy Body Weight • In most cases, folks who meet all of these criteria may not gain a health advantage by changing their weight. If a person does not meet all these criteria, it is advisable to consult with a health care professional to make appropriate changes to increase health.

37. Body Weight and Its Standards • Most health professionals will often compare our weight with a standard weight-for-height table or chart. • These weight-height tables although commonly used, are not the best recommended method of evaluation. Instead, body mass index is used as a base line to help assess a person’s body weight and to help monitor body composition changes over time.

38. Body Mass Index • Body mass index (BMI) describes our relative weight for our given height: • BMI = Weight (kg) Height (m)2

39. BMI • Weight classifications based on BMI are based on the following: • A healthy weight in most cases falls between a BMI of 18.5 and 24.9, with under weight below 18.5 and overweight being above 25 • The average BMI of adults in the U.S. is 26.5 showing that many of us here are becoming over-weight.

40. BMI • We must be careful when considering Body Mass Index. • BMI calculations reflect height and weight measures only and not body composition. For example, a football player or weight-lifter may be classified as being overweight by BMI standards and not be over fat. Many professional athletes have higher BMI measurements but are very healthy.

41. Body Fat and its Distribution • Twhat is the ideal amount of body fat? It depends partly on the individual. A normal weight male may have between 12-20% body fat. Women, because of their greater quantity of essential fat (needed have children), usually have fat levels between 20-30%.

42. Some People Need Less • Athletes usually have a lower percentage of body fat often having enough fat to provide needed fuel, insulate and protection for the body. Also to assist with normal nerve functioning and to support hormonal activity without having too much fat to burden them with excess bulk.

43. Some People Need Less Fat, Some People Need More • Many athletes have body fat at levels of 5-10% for men and 15-20% for women. • Alaska fisherman may benefit from a higher percentage of body fat. A little extra fat can provide an insulating layer to help prevent excess body heat loss in extreme cold climates.

44. Some People Need Less, Some People Need More • Another example is a woman starting a pregnancy. she requires sufficient body fat to support conception and normal fetal growth. Below a certain threshold for body fat, hormone synthesis falters, women can become infertile, folks can develop depression, experience abnormal hunger regulation, or can have a hard time keeping warm. These thresholds different for all of us.

45. Criterion of Health • May times when asking what is nutritionally ideal for good health, some folks mistakenly turn to relying on fashion statements for the answer. • Ideally, a person should have enough fat in their diet to meet basic physiological needs but not so much fat that they develop health risks.

46. The Criterion of Health • Research has shown that health issues typically start developing when body fat exceeds ~22% in young men, ~25% in men over age 40, ~32% in young women, and at around 35% in woman over age of 40.

47. Fat Distribution • The distribution of fat on the body may be more critical than the total amount of fat in itself. Intra-abdominal fat that is stored around the organs of the abdomen is referred to as central obesity or upper-body fat. This type of fat is associated with an increased risk of heart disease, stroke, diabetes, hypertension, and some types of cancer.

48. Fat Distribution • Abdominal fat is commonly seen in women past menopause and it is even more common in men. Even when total body fat mass is similar, men usually carry more abdominal fat than either premenopausal or postmenopausal women. Regardless of menopausal status, the risks of cardiovascular disease, and mortality are increased for women with high levels of abdominal fat. The same is true for men.

49. Fat Distribution • Interestingly, fat stored around the hips and thighs, sometimes referred to as lower-body fat, is more common in women during their reproductive years. • Research shows this type of fat is relatively harmless. In fact, people who are overweight, but do not have excessive fat around the abdomen, are less susceptible to health issues than over-weight people with central obesity.

50. Waist Circumference Matters • The most valuable and practical indicator of fat distribution in the body and abdominal fat is a person’s waist circumference. In general, women with a waist circumference of greater than ~35 inches and men with a waist circumference of greater than ~40 inches have a higher risk of central obesity-related health issues.