Positive energy balance and disease

Question 1

ways to prevent obesity: exercise v diet

Answer 1

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

Question 2

600-700kcal/day weight loss manageable - under what you require

Answer 2

4500 kcal/week

1kg fat = 9000kcal

0.5 kg/week or 13kg over 6 months

Question 3

how much weight loss is adipose tissue?

Answer 3

75-90%

Question 4

how much weight loss is FFM?

Answer 4

10-25%

Question 5

what does losing weight require?

Answer 5

a change in lifestyle

commitment of patient to change

Question 6

dietary advice on diet

Answer 6

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

Question 7

orlistat mechanism of action

Answer 7

inhibits fat digestion and absorption

Question 8

side effects of orlistat

Answer 8

fat appears in faeces, may cause faecal leakage

Question 9

who is orlistat recommended for?

Answer 9

BMI > 30/>27 with co-morbidities

Question 10

prior requirement for use of orlistat

Answer 10

should have managed some previous weight loss

Question 11

weight loss expected with orlistat

Answer 11

5% at 3 months (but unsustainable)

Question 12

LT prospects with orlistat

Answer 12

maintenance of loss rarely achieved

Question 13

bariatric surgery

Answer 13

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

Question 14

example of energy overnutrition disease: type 2 diabetes

Answer 14

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

Question 15

% of body fat to classify as obese

Answer 15

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

Question 16

requirements for type 2 diabetes - waist circumference

Answer 16

Men > 102 cm

Women > 88cm

Question 17

requirements for type 2 diabetes - waist to hip ratio

Answer 17

Men > 0.9

Women > 0.85

Question 18

requirements for type 2 diabetes - % tissue fat

Answer 18

NAFLD > 5%

Indvs who are good at storing fat within adipose tissue tend not to develop type 2 diabetes

Question 19

what is the liver overspill hypothesis?

Answer 19

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

Question 20

glycaemic index

Answer 20

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

Question 21

blood glucose response to 75g glucose in indv with type 2 diabetes

Answer 21

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)

Question 22

what are type 2 diabetes patients for most of the day?

Answer 22

hyperglycaemic

Glucose concentrations over 24h in 11 patients with type 2 diabetes (upper curve) and 11 healthy control subjects (lower curve)

Question 23

nutritional strategies for diabetes

Answer 23

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)

Question 24

how can type 2 diabetes be reversed?

Answer 24

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:

Question 25

skeletal muscle glucose uptake

Answer 25

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