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Flashcards in Adaptive Thermogenesis And Set-Point Deck (44):

Minnesota semi-starvation study and 8 results

1944 - 36 males on 24 was of energy restriction and 5km run /day
- reduced basal metabolic rate
- increased hunger
- irritability
- reduced pulse
- increased sensitivity to cold
- lethargic
- obsession with food - invest in cookbooks when they had no prior interest
- hyperphagia in reseeding - increased caloric consumption


Can you just give someone leptin

No because they will develop a resistance


Why does leptin reduce?

Reduced body weight because it is proportional to fat mass


Who can we give leptin to?

People who has lost weight to remain there but you wont eat as much


Mediterranean diet and fat

All of it is bad for you and are linked to CV diseases


5145 participants with overweight/obesity - 2 groups and results

Diabetes support and education - 3 meetings/year to discuss diet, PA and social support

Intensive lifestyle intervention - meet weekly, 1200-1800kcals, meal plans, >175 weekly PA, cognitive behavioural therapy by dietitians, psychologists, and exercise specialists

Significant body weight reduction in intervention group but weight increased as time went on


204 participants with obesity and 2 weight loss programs based on time

See is we can trick the brain with a longer period of trying to lose weight - no losing weight slowly does not protect against weight regain - 15% of body weight was lost over 2 different time periods - trajectory of weight gain is the same for both
Phase1: 36 wks vs 12 wk weight loss
Phase2: if 12.5 weight loss was achieved, individuals placed on weight maintenance diet and followed for 144 weeks


Long term persistence of hormonal adaptations to weight loss - are the changes in satiety hormones that occur with weight loss persist with prolonged maintenance of reduced weight
- what happened
- participants
- avg weight loss

Satiety hormone response to meal were measured 3 times - before weight loss, after 10% weight loss, after a year of sustaining that
BMI 35 - specific meal and 180 min after the meal they measure hunger, appetite, blood test
16/50 participants didn’t complete it, 4 withdrew within the first week, 7 did not meet the 10% weight loss threshold, 5 withdrew during maintenance
Average decrease fo weight was 14 %, ~ 9 % was remained at significant at 62 wks


3 Results of the Study for persistence of Hormonal Adaptations after a year
2 conclusions

Circulating Leptin, Peptie YY, CCK, GLP- 1 and insulin were significantly reduced relative to baseline - weight loss of 13.5kg, anthro measurements were all down and remained down till wk 62 leptin decease by 65% at wk 10 - and 35 at wk 62
Circulating levels of ghrelin were significantly increased at wk 10 and 62 relative to base line
Subjective appetite - increased hunger and appetite
* homeostatic alterations that occur with negative energy balance and reduced weight persist for periods greater than one year even when weight is regained.
High recidivism rate in obesity has a strong physiological and metabolic basis


Why do the altered hormones persist at weight loss?

Body is protective of set point set by your hypothalamus


Ensure/boost/meal replacements/sports drinks

Depends on what you’re doing - if you are replenishing for an event coming up vs you’re not...


Rosenbaum and Leibel’s adaptive thermogenesis in humans
- parameters

Hospital for 9 months, liquid diet (40% fat, 45% sugar, 15% protein) and PA controlled


Adaptive thermogenesis

Decreases in energy expenditure beyond what could be predicted from body weight or its components (fat-free mass and fat mass) in response to a decrease in energy intake


Reduction in body weight and reduction in energy expenditure - does it occur in lean ind? Why? (2)

10% = 20-25% -> 10-15% lower than expected
Yes - you can be at the same body weight but your energy expenditure will be lower if you had lost weight, hunger hormones and hedonic response are amplified forever


How to win the battle?

Don’t gain weight because even if you lost it its hard to keep it off


4 mechanisms of adaptive thermogenesis

Reduction in total energy expenditure - b/c non resting energy expenditure is reduced (85-90%) and skeletal muscle work efficiency is increased by 20%
Reduced sympathetic nervous system tone (HR, metabolism) and increased parasympathetic system
Reduced thyroid hormone (T3 - active form of thyroid hormone which would have made metabolism more efficient)
Reduced brown fat


Resting energy expenditure is when?

You are unconscious


How does mechanical efficiency affect adaptive thermogenesis (3)

Improved through reduced energy expenditure for a set amount of work - less oxygen required
- increased utilization of FA as a fuel
- reduction in glycolysis (decreased phosphofructokinase activity)
- decreased PFK/cytochrome oxidase (COX) ratio - indicating increased fat oxidation


Adaptive thermogenesis and brown fat

Weight loss -> reduction in brown adipose tissue who produces heat
- due to reduced SNS &/ reduced thyroid hormone


Mechanism of brown fat

More mitochondria and uncoupled protein 1 (UCP-1) - uncouple of mitochondrial substrate oxidation from ATP production - release the energy of FA as heat.


Weight loss and PAexercise

Need to be uncoupled


Metabolism of biggest losers

Slower and weight is back up, EE stays low so you cant eat the same amt of calories


Adaptive thermogenesis to weight gain

Increased thyroid hormone
SNS activated
TEE, NREE, leptin goes up
*for a period of time - 3/4 wks this will become your new set point and hypothalamus will kick in and protect that set point for your body


Does increased hunger and appetite after weight loss diminish over time?



TEE and weight loss

Disproportionate decrease in TEE after weight loss.


Does the body like to lose weight? Why?

No - survival, extra energy/certain amount of body fat for reproduction - thus why leptin is so important


How do you keep your weight off?

Whatever you did to get rid of it you must maintain for the rest of your life to maintain that weight loss.


What do western societies regard obesity and inability of ind to sustain weight loss

self-imposed conditions that reflect a lack of will power related to lifestyle changes


Why is there a tendency to store energy as fat? (2) how?

- advantage by enabling survival during periods of prolonged energy restriction
- nourish both mother and fetus during and after pregnancy
- human genome would be enriched for alleles of genes favoring the storage of energy as adipose tissue


in long term studies of weight reduced children and adults - how many return to their previous weight percentile?



why is there an inability to successful maintain weight loss?

reflect actions of potent and redundant metabolic, neuroendocrine and autonomic system


TEE in subjects who have sustained weight loss for extended periods of time (6m-7y) in circumstances of enforced energy restriction in the biosphere 2 project, bariatric csurgery and lifestyle modifications and what does it imply?

reduced - necessity for long term changes in lifestyle


REE changes after weight loss

some have none, some have modest reductions - 10-15% decline in TEE beyond that predicted on the basis of body composition changes


circulating leptin according to diet weight loss

decreased as it is proportional to fat mass


the fact that NREE is a major component affected by changes in body weight implies that

PA is successful in maintaining reduced weight


the lack of increase in TSH with weight loss despite the decrease in T3 means?

Hypothalamic TRH decreased following weight loss


What does the decline in SNS tone mean?

hypometabolic state - direct effects on skeletal muslce, indirect effect on circulating conc of thyroid hormones


anatomy of brown fat

rish sympathetic nerve and vascular supply


brown fat in the presence of cold, weight gain, and/or sympathetic nervous stimulation in rodents / exogenous/endogenous hypercatecholaminemia in humans

activity increases and produce heat


What causes the reduced obligatory and/or facultative thermogenesis by brown fat - 2

declines in SNS activity and circulating concentration of bioactive thyroid hormones after weight loss - could attribute to a fraction of REE change


What ultimately creates the optimal biological circumstances for weight regain? 1-2

dynamic weight loss - youre hungerier (eat more often), less satiated (eat more/meal). maintenance of reduced weight - satiety is diminished along with energy expenditure.


obesity is a state in which

human body actively opposes the cure over long periods of time beyong the initial resolution of symptomatology.


for hormonal changes following weight loss, was there change every week?



to reduce weight below the elebated body weight set point in obese persons

vigorously resisted