Causes of Obesity

– Nurture versus Nature

Nurture Theories

•Eating to satisfy : Eating to satisfy :

• Boredom Boredom • Parents Parents

• Stress Stress

• CultureCulture

• Effect of ageEffect of age

• Ego Ego

Most obese adults were slim when youngMost obese adults were slim when young

Obesity may be caused by phycologyObesity may be caused by phycology

Nature Theories

Obesity caused by physiology Dieting does not help

Ageing

Muscle tone Muscle tone

Diet induced Thermogenesis

Glycogen storage variations

Need large food intake to maintain Nitrogen BalanceNeed large food intake to maintain Nitrogen Balance

Benefits of Obesity

Obese people do not get Obese people do not get osteoporosisosteoporosis.

This may be due to their higher insulin secretion reducing This may be due to their higher insulin secretion reducing

calcium lost in the urine. calcium lost in the urine.

Why Dieting Doesn't WorkWhy Dieting Doesn't Work Reduced energy intake causes the Reduced energy intake causes the

body to adapt:body to adapt: lowers “basal metabolismlowers “basal metabolism””

burns up fatburns up fat

reduces energy using tissuereduces energy using tissue

– lean body mass lean body mass

When you go off the dietWhen you go off the diet

use less energyuse less energy

get fatter than beforeget fatter than before

Transport of Lipids in BloodTransport of Lipids in Blood

Lipids are insoluble in water and Lipids are insoluble in water and blood fluidsblood fluids– must be carried with proteins called must be carried with proteins called

LipoproteinsLipoproteins

LipoproteinsLipoproteins ChylomicraChylomicra carry fat from carry fat from

Intestine to tissueIntestine to tissue LDLLDL ( low density lipoprotein) ( low density lipoprotein) carry lipids from Liver to tissuescarry lipids from Liver to tissues VLDLP loose fatty acids to tissues they VLDLP loose fatty acids to tissues they

get denser and become get denser and become IDLPIDLP and and eventually eventually LDLPLDLP then then Reminant Reminant LDLPLDLP and chylomicra return to and chylomicra return to liverliver

HDLHDL carry cholesterol from tissues carry cholesterol from tissues to liverto liver– known as known as Revers transportRevers transport

LipoproteinsLipoproteins

Chylomicra

Intestine

Liver

Body tissues

VLDLP

HDLPLDLP IDLP

Danger of Excess Dietary Danger of Excess Dietary Fat -Fat -

CancerCancer Undigested fatty acids reaching Undigested fatty acids reaching

the colon stimulates cancerthe colon stimulates cancer fatty acids make soap that wash of fatty acids make soap that wash of

cells off the lining the gutcells off the lining the gut This acts as a MITOGEN ie This acts as a MITOGEN ie

stimulates cell growthstimulates cell growth Cancer needs two stages to start:Cancer needs two stages to start:

• Mutagen and then mitagenMutagen and then mitagen

Danger of Excess Dietary Danger of Excess Dietary FatFat

Increases cholesterol productionIncreases cholesterol production– imbalance of carbohydrate and fat imbalance of carbohydrate and fat

metabolism metabolism – cardiovascular diseasecardiovascular disease

ObesityObesity DiabetesDiabetes

Cardiovascular Disease

Normal CatabolismNormal Catabolism

High Fat CatabolismHigh Fat Catabolism

Fat Carbohydrate Fat Carbohydrate ImbalanceImbalance

More fat means less carbohydrateMore fat means less carbohydrate Less anaplerosis => more cholesterolLess anaplerosis => more cholesterol Not all fat the same ???Not all fat the same ??? Unsaturated seam OKUnsaturated seam OK Long chain fatty acids seam OKLong chain fatty acids seam OK Short chain fatty acids reduce CVDShort chain fatty acids reduce CVD Medium length FA seam worstMedium length FA seam worst

Danger of Excess Dietary Danger of Excess Dietary FatFat

Increases cholesterol productionIncreases cholesterol production– imbalance of carbohydrate and fat imbalance of carbohydrate and fat

metabolism metabolism – cardiovascular diseasecardiovascular disease

ObesityObesity DiabetesDiabetes

Cardiovascular Disease

Normal CatabolismNormal Catabolism

High Fat CatabolismHigh Fat Catabolism

Fat Carbohydrate Fat Carbohydrate ImbalanceImbalance

More fat means less carbohydrateMore fat means less carbohydrate Less anaplerosis => more cholesterolLess anaplerosis => more cholesterol Not all fat the same ???Not all fat the same ??? Unsaturated seam OKUnsaturated seam OK Long chain fatty acids seam OKLong chain fatty acids seam OK Short chain fatty acids reduce CVDShort chain fatty acids reduce CVD Medium length FA seam worstMedium length FA seam worst