Positive energy balance and disease Flashcards
ways to prevent obesity: exercise v diet
1g fat = 9kcal
70kg indv running 8min/mile pace (high intensity) would expend approx. 900kcal in 1h. ½ from carb and ½ from fat - so 50g from fat
100g fat
High-intensity ex tasks usually not feasible for indvs with v. high BMI and body fat %
Energy expenditure that can be achieved through more gentle physical activity more typically < 500kcal/day
45g fat
Often compensated for by overeating after exercise – easily done
Achievable increase in energy expenditure through exercise mist be used in conjunction with reduced daily calorie intake – need to be in neg energy deficit
Exercise does not lower weight in overweight individuals
600-700kcal/day weight loss manageable - under what you require
4500 kcal/week
1kg fat = 9000kcal
0.5 kg/week or 13kg over 6 months
how much weight loss is adipose tissue?
75-90%
how much weight loss is FFM?
10-25%
what does losing weight require?
a change in lifestyle
commitment of patient to change
dietary advice on diet
Low fat, energy density, energy content and high fibre
Replace saturated with monounsaturated fat, high GI with low GI foods and increase protein (20% or greater)
V. low calorie diets (800 kcal/day for several weeks) also efficacious - thinks body is in fasting state
orlistat mechanism of action
inhibits fat digestion and absorption
side effects of orlistat
fat appears in faeces, may cause faecal leakage
who is orlistat recommended for?
BMI > 30/>27 with co-morbidities
prior requirement for use of orlistat
should have managed some previous weight loss
weight loss expected with orlistat
5% at 3 months (but unsustainable)
LT prospects with orlistat
maintenance of loss rarely achieved
bariatric surgery
Reduces energy intake to 1200 - 1500 kcal/day
> 30% weight loss in first year which is maintained for many years - low risk/mortality rate
Protein malnutrition? - stomach needed to digest proteins
Iron deficiency and vitamin D deficiency
Increases gut hormone response - patients feel full with reduced desire to eat
example of energy overnutrition disease: type 2 diabetes
1/10 of adult population
Characterised by high blood glucose levels (hyperglycaemia) due to insulin resistance
Hyperglycaemia over prolonged period damaged small blood vessels (microvascular disease, e.g. retinopathy), large blood vessels (macrovascular disease, e.g. heart disease) and nerves (neuropathy)
Not all indvs obese at time of diagnosis (75%), but vast majority have fatty livers - not caused by obesity but caused by positive energy balance
Non-dependent on insulin, but exogenous insulin will eventually be required as insulin secretion declines over time due to years of excessive production to lower glucose - pancreas starts to fail
% of body fat to classify as obese
Men > 30%
Women > 35%
Only 20% morbidly obese (>40 BMI) indvs undergoing bariatric surgery have tye=pe 2 diabetes
Some people very good at storing fat
If not good at storing fat, goes to other organs in body - type 2 diabetes = too much fat in wrong areas, stored in ab cavity and liver - causes diabetes when in liver
requirements for type 2 diabetes - waist circumference
Men > 102 cm
Women > 88cm
requirements for type 2 diabetes - waist to hip ratio
Men > 0.9
Women > 0.85
requirements for type 2 diabetes - % tissue fat
NAFLD > 5%
Indvs who are good at storing fat within adipose tissue tend not to develop type 2 diabetes
what is the liver overspill hypothesis?
With increase in fat storage, adipose tissue becomes dysfunctional and can no longer store fat as efficiently
Some indvs more likely to have dysfunctional storage than others
Fat not stored in adipose tide ‘spill over’ into other tissues such as liver and skeletal muscle
When too much fat accumulates in liver and skeletal muscle it begins to interfere with insulin action and tissues becomes ‘resistant’ to insulin
Reduced insulin suppression of glycogenolysis and gluconeogenesis in liver increase blood glucose
Reduced insulin stimulated glucose uptake in skeletal muscle increase blood glucose
glycaemic index
Glycaemic index (GI) of food relates to effect on blood glucose
Area under blood glucose x time curve for 50g glucose = 100
Low GI food < 55
High GI food > 70
blood glucose response to 75g glucose in indv with type 2 diabetes
Fasting blood glucose > 7 mmol/l diagnostic for type 2 diabetes (normal < 6 mmol/l)
Blood glucose 2h after ingestion 75g glucose > 11 mmol/l diagnostic for type 2 diabetes (normal < 7.8 mmol/l) - liver produces glucose and not being suppressed - doesn’t go back to normal after 2h
Oral glucose tolerance test (OGTT)
what are type 2 diabetes patients for most of the day?
hyperglycaemic
Glucose concentrations over 24h in 11 patients with type 2 diabetes (upper curve) and 11 healthy control subjects (lower curve)
nutritional strategies for diabetes
Lifestyle changes to improve glycaemia, dyslipidaemia and BP (salt intake)
Carb will have biggest influence on blood glucose levels, so understand basic info on carb content of meals
Keep carb consistent day-to-day, with low GI, complex carbs making up around 55-65% energy requirements
Avoid low CHO ‘fad’ diets as fruit, veg, fibre essential (diets containing > 30g fibre/day improve glycaemic control)
Limit fat to < 30% energy requirements to reduce energy intake
Sat fats < 7% total energy - replace with mono-/polyunsat fats to reduce LDL-C
Protein can increase acute insulin responses and satiating so should make up 20% diet
High protein intake may impair renal function in indvs with chronic kidney disease (0.8-1g/kg/day recommended (10-15% energy requirements)
how can type 2 diabetes be reversed?
600 kcals/day can reverse type 2 diabetes within weeks
Liver triacylglycerol content measured using magnetic resonance imaging
600kcal 2 weeks before surgery - had to shrink size of liver
600kcal diet for 8 weeks:
skeletal muscle glucose uptake
Muscle contraction also stimulates GLUT4 translocation to plasma membrane pathway independent to insulin stimulated glucose uptake and so not impaired in diabetes
Exercise potent tool to lower blood glucose levels as well as liver and muscle triacylglycerol
