energy balance NAM 2023 - Tagged.pdf

Energy Balance and Control of Body Weight MBBS stage 1 Nutrition and Metabolism Despo Papachristodoulou Body = Fat + fat free mass new born 3.4 kg 14 % fat  Body fat Wt kg %fat Male 10 yrs 31 13 Female 10...

Energy Balance and Control of Body Weight MBBS stage 1 Nutrition and Metabolism Despo Papachristodoulou Body = Fat + fat free mass new born 3.4 kg 14 % fat  Body fat Wt kg %fat Male 10 yrs 31 13 Female 10 yrs 32 19  Body fat Wt kg %fat Male 10 yrs 31 13 Female 10 yrs 32 19 Male adult 72 15 Female adult 58 28  Body fat Wt kg %fat Male 10 yrs 31 13 Female 10 yrs 32 19 Male adult 72 15 Female adult 58 28 Obese male 86 28 adult How Is Body Composition Measured? Body density Body water Total body K Methyl histidine or creatinine excretion Skinfold measurements – Biceps, triceps, supra iliac, sub scapular Mid-arm circumference  Skinfold Thickness Measurements biceps triceps supra iliac sub scapular Mid Arm Circumference  Bioelectrical Impedance electrical signal is sent through the body travels quickly through lean tissue (high % water, therefore good conductor of electricity more slowly through fat lower % water , poor conductor of electricity.) Bioelectrical Impedance devices use the information from this signal to work out body fat percentage.  The bod pod Air Displacement Plethysmography Measure volume of chamber with and without subject From subject wt and volume can calculate body density and fat and fat free mass  Energy Derived From Food kcal/g kj/g Carbohydrate 4 16.8 Fat 9.2 38.6  Energy Derived From Food kcal/g kj/g Carbohydrate 4 16.8 Fat 9.2 38.6 Protein 5.4 22.7  Energy Derived From Food kcal/g kj/g Carbohydrate 4 16.8 Fat 9.2 38.6 Protein 5.4 22.7 Alcohol 7 29.4  Energy from food Total – Heat of combustion Digestible – Absorbed Metabolisable – Digestible minus that lost in urine sweat and skin – 50% lost as heat. Less than 50% used for ‘work’  Energy requirements Energy requirement = energy expenditure Oxygen consumption proportional to Energy expenditure 1 litre oxygen : 20 kjoules Energy requirements depend on: 1. Basal metabolic rate kj/hour/kg body weight 2. Diet induced thermogenesis 3. Physical Activity sitting = 1.7BMR football = 7BMR Energy requirements depend on: 4. Environmental temperature 5. Growth, pregnancy, lactation 0.8 MJ or 200 kcal/day in trimester 3 2 MJ or 500 kcal /day in lactation infant year one, requirement 2x adult /kg bw 6. Age decrease in BMR and activity  Components of Energy Expenditure (typical 24 hour energy expenditure of 10000 kj)  Energy Balance in out no change in body mass  Intake v Expenditure Most people maintain relatively constant body weight. An increase of 10kg in 25 years amounts to an extra 5kj (1 kcal) per meal. this precision is not attained on a daily basis. Is there a set point for body weight? If so, what determines it?  Regulation of Energy Intake Hypothalamus – hunger centre? – satiety centre ? Satiety signal? Long and short term  Long term signals: SATIETY Leptin and insulin leptin signals the state of the fat stores plasma concentration reflects size of fat stores insulin signals the fullness of carbohydrate stores act in the hypothalamus through variety of neurotransmitters and neuropeptides. Inhibit hunger pathways stimulate satiety pathways  Long term signals: hunger leptin and insulin low signal need for energy hunger pathways stimulated satiety pathways suppressed Neuropeptide Y (NPY) is hunger signal Ghrelin (stomach and hypothalamus) hunger signal Pro-opiomelanocortin (POMC) related peptides, PYY 3-36 suppresses appetite Integration of hunger and satiety signals by the hypothalamus Signaling molecules are released by: stomach, intestine, adipocytes, pancreas. signals integrated in the arcuate nucleus of the brain generating the feeling of hunger or satiety + indicates stimulation - indicates inhibition Appetite control via hypothalamic neurons stomach brain NPY and AgRP stimulate hunger Ghrelin + NPY/AgRP - producing PYY3-36 intestine neurons - + POMC neurons + leptin Melanocortin peptides inhibit hunger.( Action insulin blocked by AgRP) pancreas  Short term signals from: the GI tract the hepatic portal vein the liver – They bring about the feeling of satiety through vagus and circulation What determines the last spoonful? Regulation of energy intake short term bad long term better Average weights are NOT necessarily ideal weights Body mass index = wt/ht2 (kg/m2) 18.5-24.9 Normal (ideal) 25-29.9 Overweight (pre-obese) 30-34.9 Obesity grade 1 35-39.9 Obesity grade 2 >40 Obesity grade 3  Obesity in the UK (BMI> 30) BHF, 1999 Year Women Men 1993 16.4 13.2 1994 17.3 13.8 1995 17.5 15.3 1996 18.4 16.4 1997 19.7 17  Obesity in the UK about two-thirds (66 per cent) of adults are now overweight or obese. Of these, 30 per cent are obese (2019) considerable health risk. obesity has tripled in the past 20 years and is still rising.  House of Commons Library 2022 68% of men and 60% of women are obese or overweigt  Energy intake and requirements 1990 UK Men Women Average intake: 10.3 MJ/day 7.0 MJ/day EAR 10.6 MJ / day 8.1 MJ/day The ob ob mouse normal  Causes of obesity Genetic – leptin ? (discovered 1994) – compare to ob/ob mouse – very few cases of severe obesity due to leptin deficiency or MC receptor deficiency or other single gene defect (and they act through increased appetite) – Leptin concentrations usually higher in obese people and they do not lose weight with leptin injections – Leptin resistance  Relationship between serum leptin concentrations and percentage body fat in 179 subjects with a wide range of obesity (Massachusetts Med Soc 1996)  Causes of obesity Energy expenditure, Metabolic rate? Basal metabolic rate MJ/day lean 6.1 moderately 6.7 obese obese 7.6 Total metabolic rate was also higher in the obese  Causes of obesity Socio-economic, cultural – obesity in lower socio-economic class in the UK and the Western world – in affluent classes in poorer areas of the world – lifestyle and eating habits and different perception of desirable size and status – (Image of obese in the west)  Causes of obesity Endocrinological – rarely – adrenal hyperactivity – hypothyroidism – type 2 diabetes is a result of, not a cause of obesity  Causes of obesity Physical activity – children spend 65% less energy than 25 years ago. – food intake has not decreased proportionally  Microbiota Evidence that GI tract of lean subjects has more diverse microbiota than obese Faecal transplants from obese to lean have resulted in obesity and vice versa How?  microbiota Some gut microbes digest components of fibre Produce butyrate , colonic cell proliferation and maintenance of healthy gut barrier Produce propionate, stimulates PYY production by colonic cells and decrease appetite  FTO FTO gene 2 oxoglutarate dependent dioxygenase Subjects with 1 gene 1.5 kg heavier 2 genes 3 kg heavier NIH People with “high-risk” FTO genotypes exhibit preference for high-fat foods, reduced satiety responsiveness, and greater food intake consistent with impaired satiety.  Risk factors for obesity low level of education chronic disease little physical activity heavy alcohol consumption getting married giving up smoking (Finnish study 1991)  Conditions caused by or associated with obesity Cardiovascular disease – relative risk MI 1.9 – angina 2.5 – stroke 3.1 – venous thrombosis 1.5 Diabetes mellitus type 2. Insulin resistance (2.9)  Hypertension (2.9) respiratory problems gall bladder stones (2) osteoarthritis in weight bearing joints (11.8) reduced fertility in men (decreased androgens) polycystic ovary syndrome breast, endometrial, colon & prostate cancers  Therapy: diets. Which diet? All diets work if energy intake is restricted if adhered to. Fad diets are at best harmless and often metabolically undesirable >80-% of dieters regain weight MR decreases in starvation by 15-30%. Intake has to decrease accordingly – rats after 4 days without food need 60% of normal intake to maintain their weight  Which diet works best? High protein diets often easier to follow because of satiety value of protein v carbohydrate or fat Should include wholegrain cereals and fruit and vegetables longer term  Keto diet Primarily used to reduce frequency of epileptic seizures in children As a weight loss regime (Harvard and Mayo advice:) High saturated fat content in most keto diets may be of concern. Protein should be very limited to allow the liver to produce ketones Initially water loss and some fat loss but no more successful than other E restricted diets after one year  Intermittent fasting Claims: Improve thinking Heart Type 2 diabetes and obesity Most studies on animals Human studies show no benefit compared to continuous restriction of calories.  Therapy: pharmacological Uncouplers and thyroid hormone treatment dangerous and have been lethal (withdrawn) Sibutramine increases conc of serotonin and tends to reduce appetite (now withdrawn) Orlistat* decreases fat absorption leptin modest effect at high doses but obese have leptin resistance * = licenced in the UK  NIH: Many diet and exercise trends have origins in legitimate science, though the facts tend to get distorted by the time they achieve mainstream popularity. Benefits are exaggerated. Risks are downplayed. Science takes a back seat to marketing  Surgery Liposuction Resection of intestine Stomach stapling Stomach banding Complications common, maintenance difficult My gastric band was worth every penny!