Download File - SMIC Nutrition Science

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Discussion Questions – Energy Balance
1. When might someone want or need to be in positive or negative energy balance?
2. How does the number of adipocytes in a person’s body impact on his/her ability to avoid obesity? How
can a person minimize the number of adipocytes he or she has?
3. What are the pros and cons of resorting to surgical procedures to promote weight loss?
4. What regulates hunger and satiety? What can an individual do to increase his/her own sensations of
each?
5. Why do some people eat primarily in response to hunger while others eat in response to appetite and/or
cravings? How likely is each group to eat nutrient-dense foods?
6. What parameters are considered in helping someone estimate his/her energy expenditure?
7. Why is it important to assess body composition as well as body weight?
8. What lifestyle, socio-cultural, and genetic factors influence food preferences, dietary practices, and
whether or not someone becomes obese?
9. What role does physical activity have in maintaining fitness and a healthy body weight?
10. Why does most people’s weight remain stable over time?
11. What changes in supermarket choices and the food-away-from-home industry might have a positive
impact on the nutrition and health of U.S. residents?
12. What are the hallmarks of “healthy” and “likely-to-be-successful” weight management regimes?
13. What practical suggestions might you make to anyone wanting to increase his/her energy expenditure?
14. What is the best balance of nutrients for achieving weight loss?
15. Is a low-carbohydrate diet safe and effective for losing weight?
1. When might someone want or need to be in positive or negative energy balance?
Answer (key points): Positive energy balance occurs when energy intake > energy expenditure.
Negative energy balance occurs when energy intake < energy expenditure. In most cases, weight change
is a good indicator of energy balance: Weight gain indicates positive energy balance, weight loss
indicates negative energy balance, and no change indicates energy balance.
Positive energy balance is desirable during periods of growth such as infancy, pregnancy, and intense
weight training to increase muscle mass. Negative energy balance is the goal for individuals who want to
lose weight. (p. 323)
2. How does the number of adipocytes in a person’s body impact on his/her ability to avoid obesity? How
can a person minimize the number of adipocytes he or she has?
Answer (key points): Some scientist believe that the number and size of adipocytes may influence the
ability to maintain a healthy weight. People with fewer, enlarged adipocytes may have less difficulty
maintaining weight loss than those with a greater number of smaller adipocytes. Avoiding excessive
weight gain can help minimize one’s adipocyte population, since in adults new adipocytes are not
formed until existing ones are full of stored lipids. Once the number of adipocytes has increased, it
usually remains higher than before despite any subsequent weight loss. (pp. 323-324)
3. What are the pros and cons of resorting to surgical procedures to promote weight loss?
Answer (key points): Pros: Improved quality of life both physically and emotionally. A recent study of
4,000 obese subjects showed significant improvement in survival rates in obese individuals. Gastric
bypass surgery may help lower death rates associated with type 2 diabetes, heart disease, and cancer.
Cons: heartburn, abdominal pain, and vomiting. Increased risk of nutritional deficiencies, dumping
syndrome, and other complications from surgery. Death rate within one year of surgery is 1%-5%. (p.
327)
4. What regulates hunger and satiety? What can an individual do to increase his/her own sensations of
each?
Answer (key points): Hunger and satiety are influenced by concentrations of glucose, amino acids, and
lipids in the blood. Elevated blood glucose, amino acids, and lipids promote satiety. Decreased levels of
glucose, amino acids, and lipids release neurotransmitters that stimulate hunger. The presence of food in
the stomach and small intestine can trigger the release of GI hormones (CCK, PYY)—the majority of
which promote satiety. Ghrelin is one of the few that doesn’t promote satiety but appears to signal
hunger to the brain. (pp. 325-327, 328-329)
5. Why do some people eat primarily in response to hunger while others eat in response to appetite and/or
cravings? How likely is each group to eat nutrient-dense foods?
Answer (key points): “Some people eat to live and others live to eat.” People who eat primarily in
response to hunger are responding physiologically to the need to meet their energy needs. People that eat
in response to appetite or cravings are responding psychologically and may or may not physically be
“hungry” or be in an energy deficit.
People who eat because of appetite, if they are influenced by food cravings, may be more prone to eat
calorie-rich, less-nutrient-dense foods high in refined carbohydrate and/or fat. For those who eat in
response to cravings, new information on the role of neurochemicals is becoming available. Hormones
are thought to be involved, since food cravings are more common in women, especially during
menstruation or pregnancy. (pp. 325, 329-331)
6. What parameters are considered in helping someone estimate his/her energy expenditure?
Answer (key points): Total energy expenditure (TEE) takes into account three components: (1) basal
metabolism, (2) physical activity, and (3) thermic effect of food. As it is too difficult to measure basal
metabolism because of the stringent conditions required, resting metabolic rate (RMR) is often used.
RMR expressed over 24 hour period = resting energy expenditure (REE). The Harris-Benedict Equation
can be used to calculate REE. The DRIs developed by Institute of Medicine include calculations for
Estimated Energy Requirements (EERs) that take into account TEE and energy to support growth. EERs
for adults are intended for weight maintenance. Adjustments in energy intake and physical activity can
be made to support weight loss or gain. (pp. 331-332, 335)
7. Why is it important to assess body composition as well as body weight?
Answer (key points): A person’s weight does not provide information about body composition—i.e., %
lean muscle mass, % body fat, and body water. It would be particularly helpful to assess body
composition, as it changes throughout the life cycle and is affected by health status, diet, and overall
energy balance. It is possible for physically fit people to weigh more and appear “overweight” or
“obese” when they are actually lean. Muscle is more dense than fat; thus, the more muscle mass a person
has, the more dense he/she will be and the more he/she will weigh. (pp. 337-339)
8. What lifestyle, socio-cultural, and genetic factors influence food preferences, dietary practices, and
whether or not someone becomes obese?
Answer (key points): The obesity epidemic in the U.S. is multi-factorial. One major contributing factor
is an increase in energy intake over the last few decades (200-300 kcal/day). Societal influences on
eating include number of meals, eating outside the home, increased portion sizes, increased consumption
of energy-dense foods, and changes in snack habits. Socio-cultural and psychological factors such as
differences in income, education, dietary beliefs, and acceptability of being overweight can increase risk
of obesity. Psychological influences such as family and the social environment can provide permissive
cues for others to gain weight. People who are depressed, anxious, or impulsive, have low self-esteem,
or have suffered emotional trauma may turn to food for emotional comfort, making them more likely to
suffer from obesity. Genetics can predispose individuals to becoming obese (or not) in response to these
socio-cultural and lifestyle factors. (pp. 341-345)
9. What role does physical activity have in maintaining fitness and a healthy body weight?
Answer (key points): Physical inactivity has contributed to the growing rates of obesity—most
worrisome are rates among children and adolescents. Inactivity has been studied extensively in this age
group (television viewing, video games, and computers). This trend is changing and opportunities to
increase physical activity are increasing. New physical activity recommendations for adults released by
the U.S. government recommend that adults engage in at least 150 minutes/week of moderate-intensity
or 75 minutes/week of vigorous-intensity aerobic activity, plus moderate- or vigorous-intensity musclestrengthening activities on 2 or more days/week. According to an International Association for the Study
of Obesity expert panel, daily exercise assists in prevention of weight gain among adults. (pp. 344-345,
352-353)
10. Why does most people’s weight remain stable over time?
Answer (key points): Scientists have long suspected that a complex signaling system regulating body
weight exists in humans. To test this theory, researchers observed weight gain and weight loss cycles in
mice. When food-restricted, mice lost weight. When taken off food restriction, the mice increased their
food consumption and soon returned to their original weight. Once the mice returned to their original
weight, their consumption dropped off. This phenomenon was termed the set point theory of body
regulation. Adipose tissue is now known to be a very active tissue that responds to factors circulating in
the blood and communicated to the brain. When adipose tissue increases beyond a “set point” in humans,
it is believed that a signal causes food intake to decrease and/or energy expenditure to increase to
promote weight loss. On the other hand, if adipose tissue stores decrease below a “set point,” food intake
increases and energy expenditure decreases, favoring weight gain. Ultimately, body weight is set and
remains relatively stable. (p. 348)
11. What changes in supermarket choices and the food-away-from-home industry might have a positive
impact on the nutrition and health of U.S. residents?
Answer (key points): Being able to choose salads and sandwiches made with lean meats and wholegrain breads. Purchasing 100-kcalorie snack packs, pre-portioned items, and other reduced-kcalorie,
portion-controlled foods. Having an assortment of low-fat single-serving dairy products such as yogurts,
low-fat cheese sticks, and frozen pops/ice cream (low in added sugars) available. Providing conveniently
packaged or easy “grab ‘n’ go” fruits and vegetables. (pp. 351-352)
12. What are the hallmarks of “healthy” and “likely-to-be-successful” weight management regimes?
Answer (key points): They require making lasting lifestyle changes—most importantly food choice and
physical activity. The focus should be more on healthy eating and becoming more physically active and
less on “dieting.” The hallmarks are: (1) set reasonable goals, (2) choose nutritious foods in moderation,
and (3) increase energy expenditure by daily physical activity. (pp. 351-353)
13. What practical suggestions might you make to anyone wanting to increase his/her energy expenditure?
Answer (key points): Increasing energy expenditure requires becoming physically active. Physical
activity can be incorporated into a person’s daily routine—e.g., taking the stairs instead of the elevator,
walking or biking instead of driving, and daily chores. Leisure activities that include physical activity
such as a hike, bicycling, or a ski trip can be a fun way to contribute to increasing energy expenditure.
Regular planned exercise can go a long way to promote an increase in energy expenditure. The most
important thing to consider about planned exercise is that the exercise be something that is enjoyed and
varied often to avoid monotony. (pp. 352-353)
14. What is the best balance of nutrients for achieving weight loss?
Answer (key points): No consensus. It appears that weight loss reported is due to kcalorie reduction
rather than to a direct effect of the manipulation of the macronutrient composition of the diet. (pp. 353358)
15. Is a low-carbohydrate diet safe and effective for losing weight?
Answer (key points): A recent study evaluated the effectiveness and safety of low-carbohydrate weightloss diets, reporting that a low-carbohydrate diet was an effective alternative to low-fat diets and a
Mediterranean diet with little loss of lean tissue and no harmful effects on bone health. Those following
a low-carbohydrate diet lost on average of 10 lbs. after 2 years and had improvements in blood lipid
levels and glucose levels when compared to participants consuming the low-fat diet and Mediterranean
diet.
Due to the high protein intake, a low- carbohydrate diet is not advisable for people with impaired kidney
function. Of concern is the restriction of healthy high-carbohydrate foods such as fruits, vegetables, and
whole-grains. Low-carbohydrate diets may lack essential micronutrients, dietary fiber, and beneficial
phytochemicals.
A low-carbohydrate diet consists of limited food choices due to restricted carbohydrates, and appetite is
decreased with ketosis. Thus, overall kcalorie reduction is most likely the cause for the weight reduction
and not the body burning energy more efficiently. (pp. 357-358)