31 the age coefficient b 7 005 kg in the pre diction

This preview shows page 6 - 7 out of 9 pages.

31 The age coefficient ( b 7 0.05 kg) in the pre- diction equation of this population-based study was similar to the age coefficient in our male equation ( b 7 0.07 kg). These low coefficients may help explain the apparent contra- dictions in the literature about the effect or no effect from baseline age. If there is an age interaction, the age contribu- tion is either insignificant or very small, particularly in comparison to starting weight and exercise level. One explanation for the gender difference in the T1 age effect is the cross-sectional association between weight and age. The correlation between T1 age and weight for men was low, 0.06 (95% CI : 7 0.04 – 0.17) while the same correlation for the women was higher, 0.17 (95% CI: 0.02 – 0.32). To study this more closely, we examined the cross-sectional aging effect of weight with two large NASA databases used to study the role of aging in VO 2max . 22,23 The correlation between age and body weight for over 1500 NASA male employees (aged 25 – 70 y) was 0.05 (95% CI : 7 0.01 to 0.10). In contrast, the correlation found with 407 NASA women who ranged in age from 20 to 64 y was higher, 0.25 (95% CI: 0.16 – 0.34). This suggests that the failure to find a T1 aging effect with women is that of a gender difference in the cross-sectional aging effect on body weight. The T1 weight of women is somewhat reflective of their age. As a predictor of future weight (ie T2 weight) of women T1 weight is more potent than age. Multiple regression of our data revealed that physical activity level is a significant source of weight change, but differential effects should be expected based on initial weight and gender. For the same level of physical activity, heavier men and women exhibit the most favorable changes in body weight. For equal weight loss over time, individuals with lower T1 weights need to exercise more than heavier indivi- duals. The high value of T1 weight in predicting T2 weight may be explained by the fact that the energy cost of exercise is largely dependent on body weight. For example, metabolic calculations 32 show that, in a mile of walking, a 90 kg person (198 lb) will burn about 439 kJ (105 kcal), but a 70 kg person (154 lb) walking the same distance will burn only 335 kJ (80 kcal). This may be one of the reasons why overweight people tend to lose a substantial amount of weight with exercise early on and then lose smaller amounts of weight over time. For example, a 90 kg person (198 lb) walking 20 miles per week burns enough energy to lose 0.45 kg (one pound) in about 1.7 weeks. The time required to lose the same weight with this walking regimen is about 1.9 weeks for an 80 kg individual (176 lb) and 2.2 weeks for a 70 kg person (154 lb). These calculations illustrate that, as the body weight drops, the rate of loss also will drop unless the individual progressively increases the walking mileage.
Image of page 6

Subscribe to view the full document.

Image of page 7
You've reached the end of this preview.
  • Spring '12
  • fwsf
  • The Land, physical activity, International Journal of Obesity, LT Wier

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern