Energy Needs and Energy Utilization

What are the two concepts of energy balance?

• positive energy balance

• negative energy balance

What is positive energy balance?

• energy intake is more than energy expended

• weight gain from increased muscle mass and adipose tissue

• periods of growth: pregnancy, childhood, adolescence

What is negative energy balance?

• energy expended is more than energy intake

• food intake is reduced, more energy expended through activity or both

• results in weight loss

  • fat loss

  • muscle loss

  • loss of glycogen and bound water

What are the body’s energy needs for each individual based on?

• Varies for each individual based on:

  • basal metabolic rate (BMR)

  • thermic effect of exercise (TEE)

  • thermic effect of food (TEF)

  • adaptive thermogenesis

What is thermogenesis?

• production of heat by the body

  • adaptive thermogenesis: body regulation of heat production

What does energy expenditure provide?

• energy expenditure provides the basis for energy balance to maintain weight or gain/lose weight

What is BMR?

• Basal metabolic rate (BMR) is the energy that needs to be met for the body’s basic physiological needs

Why does BMR have a wide interperson variability?

• a lot of factors can influence one’s BMR

How does body composition affect BMR?

• body composition: how much our tissue are muscles vs adipose. higher amount of muscle will increase BMR

How does age affect BMR?

• age: BMR declines with age in adult years and mostly because change in body composition, not necessarily activity

How does pregnancy affect BMR?

• pregnancy: BMR increases because an energy-expensive period of time

How does biological sex affect BMR?

• biological sex: biological males have higher BMR than females due to larger body size and lean muscle tissue

How does body size affect BMR?

• body size: larger the body, the more energy needed because more surface area and more heat loss

How does genetics affect BMR?

• Similar metabolic rates within families based on genes

How does emotional and physical stress affect BMR?

• energy and protein needs are elevated during times of sickness and stress, which increase BMR

How do thyroid hormones affect BMR?

• low thyroid hormone levels: lower BMR

• high thyroid hormone levels: higher BMR

How does nutritional status affect BMR?

• starvation and fasting lower BMR

  • if not getting enough energy, the body will try to dial down the amount of energy needed to keep one alive by compromising some mechanisms

How does environmental temperature affect BMR?

• body heat regulation is metabolically expensive

How does caffeine and nicotine intake affect BMR?

• Caffeine will not significantly change how much energy needed for a day

• But nicotine and other stimulants can have more of an effect on BMR

How can you estimate one’s BMR?

• BMR is difficult to precisely measure, so resting metabolic rate (RMR) is used to estimate

In what ways does physical activity require energy?

• Thermic effect of exercise (TEE)

  • increase in muscle contraction that occurs during physical activity

• Non-exercise activity thermogenesis (NEAT)

  • energy expended from activities not considered exercise

What do the kcals needed for TEE depend on?

• depends on the activity performed, duration of activity, and how much you weigh

What is Thermic Effect of Food used for?

• Energy used for digestion and absorption

• Used to process the macronutrients and extract kcals from food

What is TEF influenced by?

• Meal composition and nutrients consumed

  • fat (lowest) < carbohydrate < protein (highest)

  • can be because of the structures (protein is more complex)

• athletic training decreases TEF

• weight status due to insulin sensitivity

How do we measure energy expenditure?

• direct calorimetry

• indirect calorimetry

How does direct calorimetry measure energy expenditure?

• measures energy expenditure by assessing body heat loss within a metabolic chamber (not accessible because $$)

How does indirect calorimetry measure energy expenditure?

• estimates energy expenditure by measuring oxygen consumed and CO2 produced with a metabolic cart

How can estimating energy expenditure be done mathematically?

• based on age, biological sex, height, weight, and level of physical activity

• Mifflin-St. Joer Equation to estimate RMR

  • based on biological sex, height, weight, and age

  • multiply this by the physical activity factor

What are involved in energy utilization?

• hormones are involved in signaling energy storage vs. usage

What does glucagon promote in energy utilization?

• glycogenolysis (in the liver)

  • breaking down glycogen to glucose to be used

• lipolysis

  • breakdown of adipose tissue to mobilize substrates used for energy

• gluconeogenesis

  • make new glucose out of non-carb substrates

What does insulin promote in energy utilization?

• glycogenesis

  • increasing storage in the liver and muscle by creating glycogen

• use of glucose by the cells, and if not used, will be stored

• lipogenesis

  • converting glucose to triglyceride

What is hunger?

• sensation indicating the physiological need for food

What is appetite?

• desire to eat with or without the presence of hunger

What is satiety?

• satiety is the sensation of fullness after eating

What are hunger and satiety controlled by?

• hunger and satiety are controlled by hormones:

  • leptin: stimulates satiety and produced by adipocytes

  • ghrelin: stimulates hunger and produced by the stomach (growling ghrelin)

Which hormones stimulates satiety?

• insulin

• leptin

• peptide (YY)

• cholecystokinin (CCK)

• incretins (GLP-1 and GIP)

  • GLP-1 receptor agonists

Which hormones stimulates hunger?

• neuropeptide Y

• ghrelin

What are the processes involved in regulating satiety?

• physiological cues prompt the release of hormones

• leptin quantity influenced by quantity of fat stores

• ghrelin stimulates neuropeptide Y’s impact on hypothalamus

  • ghrelin levels are higher between meals and during sleep

How do the release of hormones regulate satiety?

• stomach distension: stretch receptors are triggered

• detection of entrance of protein, fat, CHO into the small intestine

• hormones communicate systemically to signal satiety to the hypothalamus

What are the five components of physical fitness?

• cardiorespiratory endurance

• muscular strength

• muscular endurance

• flexibility

• body composition

What is cardiorespiratory endurance?

• ability to sustain cardiorespiratory exercise for an extended length of time

What is muscular strength?

• ability to produce force for a brief period of time

What is muscular endurance?

• ability to exert force over a longer period of time without fatigue

What is flexibility?

• range of motion around a joint

What is body composition?

• the proportion of muscle, fat, water, and other tissue in the body

What are the research-supported benefits of exercise

• impact on body composition

• reduced risk of chronic NCDs (non-communicable disease)

  • improves BP

  • increases HDL cholesterol

  • lowers risk of cardiovascular disease

  • improves insulin sensitivity

• reduced risk of some cancers

• bone health

• improved immune system functioning

• improved sleep quality

• improved mental well-being

Which kind of exercise is the best?

• includes activities based on all components of fitness:

  • cardiorespiratory endurance

  • muscular strength and endurance

  • flexibility

• tailored and individualized according to needs

• consistent

• enjoyable

What is cardiorespiratory exercise?

• typically aerobic exercise

• involves continuous activities that use large muscle groups

• measured by VO2 max

What does strength training improve? Why is it important to rest between sets?

• Improves muscle strength, muscle endurance, and body comp

  • to increase muscle strength: lower number of reps, heavier weights

  • to increase muscle endurance: higher number of reps, lighter weights

• usually anaerobic, so important to rest

What are the two principles for planning and improving?

• FITT acronym

  • frequency, intensity, time, and type

• progressive overload principle

  • body gradually adapts to activities via conditioning

  • gradually increase exercise demands by modifying F/I/T/T component

What is anaerobic energy used for? What are examples of exercises? What is the anaerobic capacity?

• fuel quick and intense bursts of exercise

• ex: strength (lifting weights), speed/sprinting, jumping

• anaerobic capacity is ~10 secs of maximal effort

• creatine phosphate

What does aerobic ATP production require?

• requires oxygen → heavier breathing increases intake

• slower pace

• no longer maximal effort

• sustains long-term

What are the preferred glucose sources?

• muscle glycogen

• circulating BG

• liver glycogen → BG

What is the primary energy source during high-intensity exercise?

• carbohydrates

  • BG

  • stored glycogen → depleted with exercise

  • dietary CHO

What are the use of glucose and glycogen affected by?

• intensity of exercise

• duration of exercise

• conditioning

What happens when you deplete glycogen stores?

• “hitting the wall”

What are the carbohydrate type(s) for exercise?

• eat simple CHO during and immediately after activity

  • absorbed quickly and enters bloodstream

  • sport drinks, gels, bananas, bagels/bread (not whole grain or high fiber)

• eat whole-grain and complex CHO several hours beforehand

  • absorbed more slowly

  • sustained source of fuel

  • too much fiber pre-workout can cause GI symptoms/discomfort

When does fat emerge as an energy source?

• fat emerges as energy source for low- to moderate-intensity activity

What does fat as an energy source require?

• requires availability of oxygen

What is protein needed for?

• primarily for muscle repair

  • small quantities of protein (amino acid) used for energy

  • exercise increases cortisol, stimulating protein turnover

  • insufficient kcal & CHO intake

What is the timing intake relative to exercise?

• pre-activity

  • allow sufficient time for food to digest before exercise

• during exercise

  • not needed

  • but if exercise > 1hr, food intake required to maintain BG levels

• post-activity

  • recovery

  • consume CHO to replenish glycogen stores

  • consume protein + CHO to increase muscle protein synthesis

What does adequate fluid intake prevent?

• prevents dehydration and electrolyte imbalances

Why is fluid needed for exercise?

• exercise induces greater losses of water and electrolytes

When is fluid loss greater?

• greater losses occur in hot, humid weather

  • increased risk of heat exhaustion → heat stroke

If activity is longer than 60 minutes, what fluid is recommended?

• sports drinks for longer durations