Bone mineral density during reduction, maintenance and regain of body weight in premenopausal, obese women.

Weight loss may lead to bone loss but little is known about changes in bone mass during regain of reduced weight. We studied changes in bone mineral density (BMD) and bone mineral content (BMC) during voluntary weight reduction and partial regain. The study consisted of three phases: a 3 month weight reduction with very-low-energy diet (VLED), a 9 month randomized, controlled walking intervention period with two training groups (target energy expenditure 4.2 or 8.4 MJ/week) and a 24-month follow-up. The participants were premenopausal women with a mean body mass index of 34.0 (SD 3.6) kg/m2. Seventy-four of 85 subjects completed the whole study. Total body, lumbar spine, proximal femur and dominant radius BMD and BMC were measured with dual-energy X-ray absorptiometry (DXA). The mean weight loss during VLED was 13.2 (3.4) kg, accompanied by unchanged total body BMC and decreased lumbar, trochanteric and radial BMD (p < 0.05). During months 3-36, an average of 62% of the weight loss was regained, total body BMC decreased and trochanteric BMD increased (p < 0.05). At the end of the study, total body BMC and lumbar and femoral neck BMD were lower than initially (p < 0.05). Weight change throughout the study correlated significantly with the change in radial (r = 0.54), total body (r = 0.39) and trochanteric (r = 0.37) BMD. Exercise-group assignment had no effect on BMD at weight-bearing sites. In conclusion, the observed changes in BMD and BMC during weight reduction and its partial regain were clinically small and partly reversible. More studies are needed to clarify whether the observed weight changes in BMD and BMC are real or are artifacts arising from assumptions, inaccuracies and technical limitations of DXA.

Prediction of change in maximal aerobic power by the 2-km walk test after walking training in middle-aged adults.

The aim was to study the 2-km walk test's accuracy in predicting maximal aerobic power (VO2max) and its changes during 15-week walking training in 108 healthy middle-aged adults. Training prescription was 65-75% of VO2max 50 min/session, four times weekly. VO2max was measured walking on a treadmill and predicted from the 2-km walk test using gender-specific equations including age, body mass index, performance time and heart rate. The difference in VO2max between the walk test and the maximal exercise test before training was -0.9 ml x min(-1) x kg(-1) (SD 4.4) in men and -2.2 (3.5) in women. The total error was from 4.1 to 4.5 ml x min(-1) x kg(-1). After training the increase in measured VO2max was 2.9 ml x min(-1) x kg(-1) more in the walkers compared to the controls. The difference between the predicted and measured changes in VO2max during training ranged from -1.8 to -1.0 ml x min(-1) x kg(-1) between the study groups except in walking men, for whom the walk test overestimated the difference. The total error was from 3.1 to 4.9 ml x min(-1) x kg(-1). The 2-km walk test can be used as a reasonably accurate field test to predict changes in VO2max due to aerobic training in healthy nonathletic adults.

Body composition assessment in lean and normal-weight young women.

Using percentage body fat (BF%) from a three-compartment (3C) model (body density from underwater weighing (UWW) and bone-mineral mass from dual-energy X-ray absorptiometry (DXA) as a criterion, we studied the accuracy of UWW, DXA, two skinfold equations, and two bioimpedance (BIA) equations. Thirty-four women (aged 16-20 years) with BF% 13.5-31.1 volunteered. UWW underestimated BF% by -0.5 BF% (95% CI: -1.0; -0.02), whereas DXA overestimated it by 7.3 BF% (95% CI 5.8; 8.8). Skinfolds underestimated and BIA overpredicted BF%. The differences between 3C and UWW, skinfolds (Durnin & Womersley, 1974) and BIA (Deurenberg et al. 1990) were dependent (range of r values: -0.63 to -0.79; P < 0.0001) on BF%, causing an overestimation of lean subjects' (UWW, BIA) or an underestimation of normal-weight subjects' (UWW, skinfolds) BF%. The 3C model and UWW gave comparable body-composition results for healthy young women with BF% of approximately 20-25. Based on a significant mean difference from the 3C model, and a large standard error of the estimate, we do not regard DXA as superior to skinfolds or BIA to assess BF%.

Resting metabolic rate and energy intake in female gymnasts, figure-skaters and soccer players.

We examined the hypothesis that lean female athletes, as compared to other female athletes and controls, have a greater deficit between reported energy intake (EI) and estimated energy expenditure (EE), and a reduction in resting energy expenditure adjusted to fat free and fat masses (REEADJ). The subjects were 12 gymnasts and figure-skaters (lean athletes), 12 soccer players (normal-weight athletes) and 10 normal-weight, untrained, controls. Body composition was calculated from a 3-compartment model (underwater weighing and dual energy x-ray absorptiometry). REE was assessed by indirect calorimetry. Physical activity and EI were estimated from 7-day records. EE was calculated using activity records and REE. REEADJ was similar in all groups (p > 0.05). EI was 8.29 (SD 1.84), 7.04 (SD 2.23) and 8.95 (SD 1.68) MJ.d-1 in controls, gymnasts and soccer players, respectively (p = 0.06). In gymnasts, reported EI was 3.19 (SD 2.63) MJ.d-1 lower than estimated EE. EI minus EE in controls was -0.18 (SD 1.80; different from gymnasts, p < 0.01) MJ.d-1, and in soccer players -0.47 (SD 1.89; different from gymnasts, p < 0.05) MJ.d-1. Low reported energy intake in gymnasts might reflect their attitudes on diet and body image.

Training effects of cross-country skiing and running on maximal aerobic cycle performance and on blood lipids.

Two experiments were carried out to compare the cardiorespiratory and metabolic effects of cross-country skiing and running training during two successive winters. Forty-year-old men were randomly assigned into skiing (n = 15 in study 1, n = 16 in study 2), running (n = 16 in study 1 and n = 16 in study 2) and control (n = 17 in study 1 and n = 16 in study 2) groups. Three subjects dropped out of the programme. The training lasted 9-10 weeks with 40-min exercise sessions three times each week. The training intensity was controlled at 75%-85% of the maximal oxygen consumption (VO2max) using portable heart rate metres and the mean heart rate was 156-157 beats.min-1 in the training groups. In the pooled data of the two studies the mean increase in the VO2max (in ml.min-1.kg-1) on a cycle ergometer was 17% for the skiing group, 13% for the running group and 2% for the control group. The increase in VO2max was highly significant in the combined exercise group compared to the control group but did not differ significantly between the skiing and running groups. The fasting serum concentrations of lipoproteins and insulin did not change significantly in any of the groups. These results suggested that training by cross-country skiing and running of the same duration and intensity at each session for 9-10 weeks improved equally the cardiorespiratory fitness of untrained middle-aged men.