weight management Flashcards
health risks of being overweight
hypertension strokes atherosclerosis arteriosclerosis increased risk of some cancers type 2 diabetes gall bladder disease angina sleep apnea liver disease (sclerosis) deep vein thrombosis and circulation problems high cholesterol gall bladder disease respiratory disorder
obesity epidemic
approx. 46% of men and 32% of women are overweight. 17% of men and 21% of women are obese.
fat cells
specialised fat cells known as ‘adipocytes’, which are concerned with storage of adipose (fat) tissue, have been linked with an individual’s susceptibility to being overweight/obese.
the size of the adipocytes and their location is believed to be genetically influenced and determined during early life - explains why to some extent, overweight adults have overweight children.
location and size of adipocytes is also believed to be the reason why some people find it difficult to shift fat from certain areas of the body, even though their overall body fat levels have dropped.
in overweight/obese people, abdominal adipocytes are metabolically more active than other areas of body - causes them to secrete proteins called adipocytokines which increases fat storage in this area.
leptin and adipocytes
there is also a physiological mechanism that also influences food intake
leptin is a peptide hormone that is active in adipocytes and has important role in regulation of metabolism and appetite.
when fat cells are full, leptin signals to the hypothalamus in the brain that adipocytes are saturated and appetite is supressed.
following a low fat and/or low calorie meal, many individuals report cravings for sweets and desserts, most of which are also high in fat. these cravings are linked to the leptin response.
rare disease where leptin gene become mutated which prevents control of appetite.
in many obese people, high levels of leptin circulating in blood have been measured, even though they still report being hungry. this is because the adipocytes of obese individuals are likely already to be saturated in fat, so leptin is continually released into the bloodstream in an attempt to suppress appetite and reduce intake of food. the repeated release and sustained exposure to leptin causes the brain to become desensitised.
dieting
calorie depravation doesn’t work for long-term weight loss.
any shortfall in energy is perceived by the body to be a threat to its survival and subsequently results in changes to the way energy is used and made available.
changes to the way energy is used and made available during dieting
- glycogen stores quickly deplete. since the brain can only utilise blood glucose for energy, reduced glycogen stores slow normal brain function making simple cognitive tasks more difficult.
- water storage is reduced because, with each gram of stored glycogen, there are almost 3g of water also stored
- atrophy of lean body mass occurs as the body attempts to make up the shortfall of energy. the amino acids that are degraded are then converted into glucose in the liver via gluconeogenesis to maintain blood glucose levels.
- additional water is lost through atrophy because each gram of stored protein stores almost 4g of water. thus, four times the weigh of protein burned is lost again from water.
- BMR is reduced significantly due to loss of lean tissue
- Ketoacidosis occurs which threatens homeostasis with increasing levels of acidity and toxicity.
- energy expenditure is also reduced because there is significant reduction in the thermic effect of feeding. when less food is consumed, there are less digestive and absorptive processes occurring.
- fat stores are conserved because they have the greatest energy value. fat also offers the body much needed insulation, especially since metabolism is dramatically reduced.
where the weight loss comes from
weight loss is inevitable when restricting calories, but under these conditions, weight loss comes from lean tissue and water - not fat!
within first 7-10 days of calorie deprivation, weight loss continues as water, glycogen and lean muscle levels continue to drop.
once the body is able to balance its energy output with the energy input of the new diet, weight loss soon plateaus.
when normal dietary practises are resumed the body’s glycogen and water stores are swiftly replenished, resulting in instant and rapid weight gain.
three techniques that can be used to control the energy balance equation with the goal of changing body weight
1) reduce calorie intake to a level below the level of expenditure.
2) maintain a caloric intake and increase the expenditure with exercise/physical activity.
3) decrease caloric intake and increase the expenditure with exercise/physical activity.
in order to maximise the amount of weight that is lost from fat in non-obese individuals, it is essential to make only modest cuts in energy intake relative to expenditure to prevent the starvation response being triggered.
weight loss is influenced by a number of variables, including
initial body weight
body composition
severity of the calorie deficit
why can obese or overweight people tolerate greater energy deficits than leaner individuals
leaner individuals are likely to lose more lean body mass and retain more fat than heavier individuals, while overweight or obese clients are likely to lose more body fat and retain more lean tissue.
how much to lose for sustainable weight loss?
most nutrition experts agree that fat loss of up to 2lbs per week, or 0.9kg is acceptable and sustainable, although 0.5-1lb is more realistic long term.
as a general rule a 3500kcal deficit a week is sufficient to see a 1lb loss.
percentage energy deficits for calories (men and women)
energy deficit males 2500 females 2000 15% M 2125 F 1700 20% M 2000 F 16000 25% M 1875 F 1500 30% M 1750 F 1400 35% M 1625 F 1300 40% M 1500 F 1200 (15% is recommended)
calculating energy content of 1 lb of body fat/adipose tissue
adipose tissue only contains 86% of fat, which reduces its energy content from 9kcal per gram to approx. 7.7kcal per gram (because regular PA and exercise allow individual to consume more food without the fear of gaining weight)
1 lb = 454g
454 x 7.7 = 3500 kcals
3500 kcals = 1 lb of body fat
guidelines for cardiovascular exercise
frequency = 3-5 times a week intensity = 55-90% of MHR or HRR (heart rate reserve) time = 20-60 mins of sustained activity type = sustained, rhythmic and large muscle group exercises like running, cycling, rowing and swimming.
guidelines to muscular fitness
frequency = 2-3 times a week intensity = 1-3 sets, 8-10 exercises, 8-12 reps, 70-75% of 1RM, 90-120 sec rest time = variable, depending on how many muscle groups are being worked type = variable, but at least two different exercises for each muscle.
