18. Tackling Obesity: Should we promote an increase in energy expenditure or a decrease in energy intake? Flashcards
We gain weight as we age. Comment on this age related weight gain. And what factors influence such weight gain?
Body weight peak around 55-60 years old. Average weight gain between the age of 20 and 55 is 11kg for both sexes. There is a positive energy balance
Discuss compensation of energy balance in terms of the 3 energy gaps
Energy gap 1 = change in energy balance to prevent weight gain - this the kcal gap you would have to set up per day to prevent weight gain.
Energy Gap 2: Change in energy balance to lose weight - a bigger gap not just to prevent weight gain but to lose some fat mass as well.
Energy gap 3: Long-term maintenance of weight loss- if you lose weight, you then need to have a certain energy intake to maintain that weight ( which will be lower than the EI you lost it at because you become more efficient).
How good is the population at maintaining a new weight after losing weight? and why?
long term studies suggest that most reduced-obese people regain nearly all of their lost weight after 5 years. Only 3% maintain it. 2/3 of those people who lost the weight regain it within a year.
Why? most people go for energy restrictions (diet) over exercise
Discuss compensation of energy balance
your energy balance is your energy intake (protein, fat, carbs) vs your energy expenditure (NEAT, exercise, TEF, BMR). If these are in balance then we maintain weight.
EI drops of you eat a low fat diet. It also drops as you reduce the amount of NEAT.
what is the relative contribution of the major organs and tissues to BMR and why is BMR important
BMR is important because it contributes to 60-75% of your energy expenditure. If this wasn’t contributing for so much then you’d have a very large energy imbalance.
Your brain, liver, heart and kidneys contribute to 58% of your BMR even though they contribute as less that 6% of your overall body weight. Skeletal muscle makes up 22% of BMR. Less that 5% is adipose tissue and the other 16% is things like skin, bone, gut etc.
Discuss the effect of diet and exercise on body weight and body composition.
- when you DIET you lose adipose tissue and some muscle
- when you EXERCISE there is some loss of adipose and then a slight gain in muscle..
There is a bigger loss in weight for dieting but this isn’t necessarily the best because you are also losing muscle. Muscle is the biggest contributor to your basal metabolic rate so we want to preserve muscle mass when losing weight and only want a loss in adipose tissue.
How does weight loss alter appetite endocrinology?
Ghrelin - increases when either dieting, or dieting and exercising to lose weight. No change for exercisers
Leptin - Decreases. The more weight you lose the bigger the drop. Biggest change in leptin when you lose weight through diet with exercise
What are the 4 mechanisms that are important to consider in dieting.
- Fat mass vs fat free mass
- Mitochondrial activity
- Triiodothyronine (T3) activity
- Glycogen (and associated water)
Explain the importance for mitochondrial activity for metabolism and losing weight
Exercise induces a dramatic transient increase in PGC-1a transcription and mRNA content in human muscle .
Dieting reduces mitochondria respiration capacity but increases mitochondrial synthesis (more mitochondria made)
Explain the importance for Triiodothyronine (T3) activity for metabolism and losing weight
dieting reduces T3 concentration so there is less drive on the metabolic rate.
Exercise does not have this effect
Explain the importance for Glycogen (and associated water) for metabolism and losing weight
Exercise reduces muscle glycogen concentration but training increases it. this means there is less glycogen in circulation and glycogen stores are replenished in the muscle.
A drop in glycogen levels may be the reason why muscle is lost during diet but not during exercise .
