Obesity, Exercise and Weight Control
HFIT 325 Exercise Physiology
American University
Reference book: Power’s 5th Edition
Obesity
OBESITY IS A MEDICAL TERM MEANING THE STORAGE OF EXCESS FAT IN THE BODY
NORMAL RANGE OF FAT %
MALE
3% - 20%, OVERFATNESS >20%
FEMALE 12% - 30%, OVERFATNESS >30%
Use BMI of ≥ 30 as obesity, 15% in 1976-1980 to 23.3% in 1988-1994
to 30.9% in 1999-2000
Review:
1. Fat %
2. Location of fat
3. Fat cell number and fat cell size
What is a desirable body weight?
It is important to think in terms of a weight range rather than a single value
T. 16.3 p446 Fox
A reasonable goal would be to achieve ‘optimal fitness’
Example: for man, percent body fat is between 12-18%
What would the corresponding body weight range be?
1. Calculate the fat weight: FW = BW X Ff
2. Calculate the fat-free weight: FFW = BW - FW
3. Calculate the desirable target weight:
FFW
TW = ---------------(1 – Fx)
BW (1 – Ff)
TW = ---------------------(1 – Fx)
FW = fat weight
BW = measured body weight
Ff = fractional expression of the percent body fat
FFW = fat-free weight or lean body weight
TW = desired target weight
Fx = fractional expression of the target percent body fat
Mr. Fittmann:
Current weight: 200 lb (90.7 kg), Percent fat: 17%, Height: 70 in (178 cm), Age: 27
Goal: to achieve ‘optimal fitness” for body composition (12-18% body fat)
What weight range would we recommend?
Step 1. FW = BW X Ff = 200 X 0.27 = 54 lb
Step 2. FFW = BW – FW = 200 – 54 = 146 lb
Step 3.
Target weight at 12% fat: TW = FFW / (1 – Fx) = 146 / (1-0.12) =146 / 0.88 = 166 lb
Target weight at 18% fat: TW = FFW / (1 – Fx) = 146 / (1-0.18) =146 / 0.82 = 178 lb
Fittmann must lose between 22 – 34lb of his 54 lb of body fat to achieve the
Recommended 12% to 18% body fat.
Also, it is not necessary that he lose 34 lb of body fat. That is merely the lower
end of the recommended range.
Energy Balance & Weight Control
Too much food
Positive energy balance
Gain weight
Quantity of food for body maintenance & growth
Body consumes its
own fat, then protein,
Loss weight
Energy needs exceed that produced from food
Negative energy balance
Energy Balance & Weight Control
Daily caloric need = BEE + GA + Ex
BEE = basal Energy Expenditure
GA = Energy Cost of General Activities (eating, walking, sitting, reading..
EX = Energy Cost of Exercise
Ross & Jackson: equations for estimating basal energy expenditure,
In calories, that takes into account age, gender, height, and weight.
Basal Energy Expenditure (BEE)
For males: BEE = 66 + (13.7 X Wt) + (5 X Ht) – (6.9 X A)
For female: BEE = 665 + (9.6 X Wt) + (1.7 X Ht) – (4.7 X A)
Wt: kg, Ht: cm, A: years
Energy Cost of General Activities (GA)
GA = BEE X 20%
Energy Cost of Exercise (EX)
Energy Cost of Exercise (EX)
Fox’s p 450, Table 16.5
Application:
Current weight: 200 lb (90.7 kg)
Fat % = 27%
Height: 70 in (178 cm)
Kcal/day= BEE + GA
BEE = 66 + (13.7 X 90.7 kg) + (5 X 178 cm) – (6.9 X 27)
= 66 + 1243 + 890 – 186 = 2013 kcal
GA = BEE X 20% = 2013 X 20% = 403 kcal
BEE + GA = 2416 kcal
This is what the subject must consume daily to maintain his current
weight at 200 lb
How to loss 22 lb ????
3500 kcal/lb X 22lb = 77,000 kcal
How long will it take him to achieve this goal?
INPUT
Reduce total caloric intake
500 kcal
500 kcal X 7 days = 3,500 kcal
3,500 + 2,700 = 6,200 kcal/w
6,200 kcal / 3,500 kcal = 1.75 lb
OUTPUT
Physical activity
For example: jogging
8.5 min/mile, 30 min/day, 5/wks
22 lb
Or
34 lb
How many weeks?
EX = (0.09 kcal/lb/min) X 200 lb X 30 min = 540 kcal/run
540 kcal X 5 session/wk = 2,700 kcal/w
22/1.75 = 12-13 weeks, 34/1.75 = 19-20 weeks