Tuesday, February 17, 2009

Fatness affects the overall oxygen delivery to working tissues but not fitness

I have grown up as a sports physiotherapist reading clinical sports medicine by Brukner & Khan. Till now this book is sort of bible to me. i am fascinated by the book and more by the author's ability to express terse subjects in explicit yet digestible manner.

when i saw a article by Karim Khan in British journal of sports medicine, i was quite eager to know what is it all about. it was fitness of fat people. Few important points are as follows:

1. changes in fitness & changes in fatness may not go side by side:
Aerobic fitness is the overall ability of the cardio-respiratory system to transport litres of oxygen to the working tissues. Any accumulation of body fat reduces the utility of this transport in terms of daily activities (including treadmill running).

To take a practical example, a man with a body mass of 70 kg and an aerobic fitness of 3.5 l/min has a relative VO2max of 50ml/[kg.min]. If that same person accumulates an extra 14 kg of body fat, the aerobic fitness may remain at 3.5 l/min. but the relative VO2max decreases to 41.7 ml/[kg.min].

Hence Units of oxygen transport can not be used to distinguish the importance of changes in fitness relative to changes in fatness.
To my experience changes in fitness precedes changes in fatness in many people under my weight loss regime especially in long term weight loss modules. Even there is non-significant weight loss there is significant changes in fitness parameters especially in aerobic fitness parameters both at physiological & biochemical fronts.

2. weight loss may not be the factor that is responsible for change in BP in a hypertensive overweight or obese going through exercises.
Exercises is prescribed as anti-hypertensive therapy. Many physicians prefer to prescribe exercises to overweight & obese hypertensive patients. However is important to determine whether an improvement of condition following exercise prescription is due to an increase in aerobic fitness, or whether it simply reflects a reduction in body fat content.

A review of 61 studies of training-induced changes in resting blood pressure concluded that any reduction in resting pressures could not be attributed to concomitant weight loss, since the changes in systolic and diastolic readings showed very small and statistically non-significant correlations with changes in body mass.

I have vividly discussed issues like this in my book "A concise text book for the management of the overweight & obese". This book was released this republic day (Jan 26) in a state level program. please have a look. for further inquiry contact:

0091-0674-2436217 (9 am-12 noon, 6pm-8pm on working days only)


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