C. Ambler et al., FITNESS AND THE EFFECT OF EXERCISE TRAINING ON THE DIETARY-INTAKE OF HEALTHY ADOLESCENTS, International journal of obesity, 22(4), 1998, pp. 354-362
OBJECTIVE: In healthy, nonobese, adolescent males and females to: (1)
Determine the relationship between fitness and energy intake; (2) asse
ss the effect of five-weeks endurance training on energy intake and fo
od choice and (3) compare food record assessments of energy intake wit
h doubly-labeled water (DLW) measurement of total energy expenditure (
TEE). DESIGN: (1) Cross sectional analysis of fitness and food intake
and (2) Prospective, randomized, controlled interventional study of en
durance-type exercise training in 44 females and 44 males (age range,
15-17 y). MEASUREMENTS: Pre and end interventional three day food reco
rds were successfully collected from 32 females (15 controls, 17 train
ed) and 39 males (19 controls, 20 trained). Fitness was assessed from
cycle ergometry as peak oxygen uptake normalized both to thigh muscle
mass and body weight. Thigh muscle mass was measured by magnetic reson
ance imaging. TEE using the DLW technique was measured in 12 females (
6 controls, 6 trained) and 20 males (10 controls, 10 trained) during w
eeks 4-5 of the exercise training program (simultaneously with the sec
ond assessment of food records). Food record data were analyzed using
the Minnesota Nutrition Data System. RESULTS: Fitness was correlated w
ith self reported total caloric intake in males but not females. In fe
males, there was a significant increase in fat intake (19.8 +/- 9%, P
< 0.05) and a significant decrease in carbohydrate intake (-9.8 +/- 4%
) in the trained subjects. No changes were observed in the control sub
jects. Energy expenditure (2072 +/- 52 kcal/d) was significantly great
er than the estimated energy intake (1520 +/- 112 kcal/d, P < 0.007) d
uring the intervention in the trained, but not control, subjects. Howe
ver, there was no weight change in either control or trained subjects.
In males, no changes were observed in food choice in either control o
r trained subjects. Similar to the females, energy expenditure (2425 /- 22 kcal/d) was significantly greater than the estimated energy inta
ke (2168 +/- 117 kcal/d, P < 0.05) during the intervention in the trai
ned, but not control, subjects. No weight changes were observed in eit
her group. CONCLUSIONS: Fitness is associated with increased self-repo
rted energy intake in males but not females, while exercise training l
ed to alterations in food selection (greater fat and reduced carbohydr
ate) only in females. These observations could reflect specific gender
differences, or, alternatively, the generally lower levels of fitness
in the females. The apparent negative energy balance without evidence
for weight loss in both the trained males and females suggests a syst
ematic under reporting of food intake during exercise programs in adol
escents, and indicates the possibility that errors in self reported fo
od intake might be greater during transitions from one level of energy
expenditure to another.