Graded associations between cardiorespiratory fitness, fatness, and blood pressure in children and adolescents

OBJECTIVE

To measure the graded relation between cardiorespiratory fitness and sum of skinfolds, waist circumference, and blood pressure in children and adolescents participating in the European youth heart study.

METHODS

The participants were 4072 children and adolescents (aged 9 and 15) from Denmark, Portugal, Estonia, and Norway. Cardiorespiratory fitness was indirectly determined using a maximal ergometer cycle test. The sum of four skinfolds, waist circumference, and blood pressure were assessed with a standardised protocol. Linear regression analysis was used to test the graded relation between cardiorespiratory fitness and the dependent variables adjusted for pubertal stage, sex, and country.

RESULTS

A significant curvilinear graded relation was found between cardiorespiratory fitness and waist circumference and sum of skinfolds (partial r2 for cardiorespiratory fitness was 0.09-0.26 for the different sexes and age groups). Systolic and diastolic blood pressure also showed a curvilinear relation with cardiorespiratory fitness, and fitness explained 2% of the variance in systolic blood pressure. The difference in systolic blood pressure between the least and most fit was 6 mm Hg.

CONCLUSION

A curvilinear graded relation was found between cardiorespiratory fitness and waist circumference, sum of skinfolds, and systolic blood pressure. The greatest difference in these health variables was observed between low and moderate fitness levels.

The association of birthweight and contemporary size with insulin resistance among children from Estonia and Denmark: findings from the European Youth Heart Study

OBJECTIVES

To assess the associations of birthweight, contemporary body mass index and height with insulin resistance in children.

DESIGN

Cross-sectional study.

PARTICIPANTS

From Estonia (n = 1174) and Denmark (n = 1018), 2192 school children aged 9 and 15 years were randomly selected.

MAIN OUTCOMES

Insulin resistance (homeostasis model assessment), triglyceride levels, high-density lipoprotein cholesterol and systolic blood pressure.

RESULTS

There was an inverse association between birthweight and insulin resistance and a positive association between contemporary body mass index and insulin resistance. With adjustment for maternal and paternal educational level, income, smoking and body mass index, an increase of one unit of sex, age and country standardized body mass index z-score was associated with a 5% (95% CI: 2, 7%) increase in homeostasis model assessment (HOMA) score and a one-unit z-score increase in birthweight with a 2% (95% CI: 0, 5%) decrease in HOMA score. In the 9-year-old age group, height was positively associated with insulin resistance [for a one-unit increase in height z-score HOMA score increased by 30% (95% CI: 14, 50%)], but in the 15-year-old age group there was no association between height and insulin resistance (4% (95% CI: -5, 14%), P for interaction with age group = 0.001). For both ages, those in the lowest third of the birthweight distribution and highest third of the body mass index distribution were most insulin resistant and, among 9-year olds, those in the lowest third of the birthweight distribution and highest third of the height distribution were most insulin resistant. Birthweight was only inversely associated with systolic blood pressure when adjustment was made for either contemporary body mass index or height and there was no association between birthweight and high-density lipoprotein or triglyceride concentrations.

CONCLUSIONS

Taken together, these results suggest that a slow intrauterine growth trajectory and/or a fast post-natal growth trajectory is associated with greater insulin resistance in childhood.

Gender and age differences in relation to the recommendations of physical activity among Norwegian children and youth

The Norwegian physical activity recommendations for children and youth state that there should be a minimum of 60 min of physical activity of at least moderate intensity every day. The purpose of this study was to evaluate objectively the level of physical activity in a representative cohort of urban children and youth in Norway with regard to these recommendations. Four hundred and ten 9-year-old and 350 15-year-old boys and girls from the Oslo region participated. Physical activity was registered for 4 consecutive days using the Computer Science and Application activity monitor. The results showed that 86.2% of the 9-year-olds and 55.4% of the 15-year-olds met the recommendations. Furthermore, the activity level was significantly (P< 0.0001) higher among boys than girls of both age groups and significantly (P<0.001) lower in the oldest cohort than in the youngest one. All participants were less active during the weekend than during the weekdays (P< 0.05). In conclusion, a number of urban children and youth do not fulfill the Norwegian physical activity recommendations, especially among the 15-year-olds. It is therefore important to provide action towards those children and youth who are least physically active and simultaneously prevent the general decline in physical activity.

[Physical activity and health--recommendations]

BACKGROUND

The health consequences of physical inactivity and the health gains of regular physical activity are briefly summarized. We present physical activity recommendations based on a review of the literature for the general adult population.

METHODS

This report employs recognised international standards for establishing causal relationships between physical activity and disease, distinguishing between four different levels: Convincing, probable, possible and insufficient evidence. Convincing or probable evidence have provided the basis for the recommendations given.

RESULTS

The total amount of physical activity (a combination of intensity, duration and frequency) is related to a number of health variables in a dose-response relationship. The preventive effect (the health gain) increases with increasing activity level, but the relationship is not linear. The greatest health gains are attained by those who are least physically fit. This applies even in old age. The health gain seems primarily to be dependent on the total energy expenditure, and less on the intensity. The dose-response relationship between physical activity levels and health gains is a continuum that does not seem to have a lower limit. Thus, any activity can be said to be better than none.

INTERPRETATION

We conclude that a minimum "target dose" that will yield substantial health gains for those who have been physically inactive for a long time, is activity of moderate intensity which corresponds to an energy expenditure of approximately 150 kcal (630 kJ) per day (or slightly more than 1,000 kcal (4.2 MJ) per week). This is equivalent to a daily walk of about 30 minutes. The activity can be divided into shorter intervals of physical activity during the course of the day, for instance intervals lasting 5-10 minutes. An increase in activity beyond this level will yield further health gains. The effect of exercise is just as good for older people as for younger people, and the same recommendations apply as to other adults.

Effect of long-term changes in diet and exercise on plasma leptin concentrations

BACKGROUND

Although it is known that plasma leptin concentrations correlate with the amount of adipose tissue in the body, little information is available on the long-term effects on leptin concentrations of changes in diet and exercise.

OBJECTIVE

We wanted to examine whether changes in dietary energy sources and exercise-mediated energy expenditure, alone or in combination, affect plasma leptin concentrations.

DESIGN

In a randomized, 2 x 2 factorial trial, 186 men with metabolic syndrome were divided into 4 groups: diet, exercise, a combination of diet and exercise, and control. Data on dietary intake, physical fitness, and demographics were collected and plasma leptin concentrations were measured before and after a 1-y intervention period.

RESULTS

Plasma leptin concentrations, body mass index, and fat mass decreased in association with long-term reductions in food intake as well as increased physical activity. By adjusting for either body mass index or fat mass, we observed a highly significant reduction in plasma leptin concentration after both the diet and the exercise interventions. There was no interaction between the interventions, suggesting a direct and additive effect of changes in diet and physical activity on plasma leptin concentrations.

CONCLUSION

Long-term changes in lifestyle consisting of decreased intake of dietary fat and increased physical activity reduced plasma leptin concentrations in humans beyond the reduction expected as a result of changes in fat mass.

[Physical activity--a crucial factor in the prevention of cardiovascular diseases]

BACKGROUND

Cardiovascular disease is a major health problem. Metabolic syndrome and type 2 diabetes increase the risk of developing cardiovascular disease.

MATERIAL AND METHODS

The articles for this review were found by MEDLINE search.

RESULTS

Regular physical activity or cardiorespiratory fitness reduces the risk of cardiovascular disease mortality in general and of coronary heart disease in particular. Existing data are convincing regarding the relationship between physical activity and cardiovascular disease, but not conclusive regarding stroke. Regular physical activity or cardiorespiratory fitness is beneficially associated with lipids, blood pressure, insulin sensitivity, obesity, haemostasis and endothelial function. An increased level of physical activity has the potential to improve these factors simultaneously. Regular physical activity decreases the risk of developing type 2 diabetes. Increased physical activity might have a beneficial effect on metabolic control in those who have type 2 diabetes.

INTERPRETATION

Physical activity should be strongly emphasised in the prevention of cardiovascular disease and type 2 diabetes.

Monday and non-Monday concentrations of lifestyle-related blood components in the Oslo Diet and Exercise Study

OBJECTIVE

We hypothesized that participants of intervention studies have an unfavourable lifestyle at the weekend compared with the rest of the week, thus affecting the concentrations of components in samples drawn on Mondays.

DESIGN

The hypothesis was examined using data from the Oslo Diet and Exercise Study, a 2 x 2 randomized intervention trial on diet and exercise involving 209 participants. Each person chose which day of the week to attend for blood sampling, both before and after the 1 year of intervention.

MAIN OUTCOME MEASURES

Comparison of mean concentrations of the components measured, in samples drawn on Mondays vs. non-Mondays, both at the start and at the end of intervention.

RESULTS

At the start, nine components, from haemostasis, carbohydrate and lipid metabolism, showed a difference of more than 10% between Monday and non-Monday values, all Monday values differing from the non-Monday values in a cardiovascularly unfavourable direction. Participants starting and ending on a Monday showed the unfavourable profile both times, and those who were examined both times on a non-Monday showed a consistently favourable profile, whereas those who changed the day of examination at the start and end changed profile accordingly.

CONCLUSION

The lifestyle-related components examined here showed differences between Monday and non-Monday values, which were not due to a selection bias. We suggest they may be related to a different lifestyle at the weekend compared with ordinary working days. If such effects are not recognized and properly taken into account, they may markedly affect the outcome of intervention studies.

Associations between central obesity and indexes of hemostatic, carbohydrate and lipid metabolism. Results of a 1-year intervention from the Oslo Diet and Exercise Study

The relationships of central obesity and physical fitness to indexes of hemostatic, lipid and glucose metabolism both at baseline and after 1 year of diet and exercise intervention were examined in 209 sedentary middle-aged men and women with increased coronary risk factor levels. Central obesity was measured as either waist circumference or waist/hip ratio. Maximal oxygen uptake was used as a measure of physical fitness. The cross-sectional results show that there were significant correlations between waist circumference and euglobuline clot lysis time (r = 0.23), factor VII (r = 0.16), glucose and insulin before and after 1 h glucose load (r ranging from 0.32 to 0.50). The 1-year intervention gave the following associations between changes in waist circumference and changes in: euglobuline clot lysis time (r = 0.27), factor VII (r = 0.19), carbohydrate variables and lipids (magnitude of r ranging from 0.19 to 0.43). Also the other indexes of obesity and physical fitness showed significant correlations to indexes of hemostatic, lipid and glucose variables, both cross-sectionally and for changes after the 1-year intervention. The associations between changes in central obesity and changes in indexes of hemostatic, carbohydrate and lipids were generally stronger during 1 year of diet and exercise intervention than those found at baseline. Multiple regression analyses with waist circumference, waist/hip ratio, percent body fat and Vo2 max as independent variables and indexes of hemostatic, carbohydrate and lipid metabolism as dependent variables showed that waist circumference was a significant predictor for indexes of the hemostatic, carbohydrate and lipid metabolism, mostly independent of physical fitness. The cross-sectional and 1-year change results support each other and therefore underscore the importance of abdominal obesity as an important risk factor for cardiovascular disease.

Lifestyle changes may reverse development of the insulin resistance syndrome. The Oslo Diet and Exercise Study: a randomized trial

OBJECTIVE

To compare and assess the single and joint effect of diet and exercise intervention for 1 year on insulin resistance and the development leading toward the insulin resistance syndrome.

RESEARCH DESIGN AND METHODS

An unmasked, randomized 2 x 2 factorial intervention trial was applied with a duration of 1 year for each participant. The trial comprised 219 men and women with diastolic blood pressure of 86-99 mmHg, HDL cholesterol < 1.20 mmol/l, triglycerides > 1.4 mmol/l, total cholesterol of 5.20-7.74 mmol/l, and BMI > 24 kg/m2. Participants were randomly allocated to diet group (n = 35), diet and exercise group (n = 67), exercise group (n = 54), and control group (n = 43). The diet included increased intake of fish and reduced total fat intake. The exercise program entailed supervised endurance exercise three times a week. Baseline cross-sectional changes and 1-year changes in insulin resistance, fasting serum levels of insulin, C-peptide, proinsulin, glucose, and lipids as well as weight, mean blood pressure, and plasminogen activator inhibitor 1 (PAI-1) values were recorded.

RESULTS

The cross-sectional results at baseline showed significant correlations between the calculated insulin resistance and BMI (r = 0.54) and correlations between the mean blood pressure (mBP) (r = 0.26) and PAI-1 (r = 0.40). The 1-year diet intervention gave a significant decrease in the calculated insulin resistance from 4.6 to 4.2 and a positive correlation between the changes in insulin resistance and changes in BMI (r = 0.40). The diet and exercise intervention also led to significantly decreased insulin resistance (from 5.0 to 4.0). The exercise intervention did not significantly change insulin resistance.

CONCLUSIONS

The cross-sectional and 1-year intervention results supported each other and underscored the important connection between increased BMI and the development leading toward the insulin resistance syndrome.

Improved carbohydrate metabolism after physical training and dietary intervention in individuals with the "atherothrombogenic syndrome'. Oslo Diet and Exercise Study (ODES). A randomized trial

OBJECTIVES

To compare the single and joint effect of 1-year diet and exercise intervention on carbohydrate metabolism and associated coronary risk variables.

DESIGN

Unmasked, randomized, 2 x 2 factorial intervention trial with 1-year duration for each participant.

SETTING

The participants were recruited from a screening examination of 40-year-old persons in Oslo, Norway.

SUBJECTS

Two hundred and nineteen sedentary men and women, with diastolic blood pressure 86-99 mmHg, HDL cholesterol < 1.20 mmol L-1, triglycerides > 1.4 mmol L-1, total cholesterol 5.20-7.74 mmol L-1 and BMI > 24. Participants were randomly allocated to control (n = 43), diet (n = 55), exercise (n = 54) and diet+exercise (n = 67).

INTERVENTIONS

Exercise: supervised endurance exercise three times a week. Diet: reduce weight, increase the intake of fish and reduce total fat intake.

MAIN OUTCOME MEASURES

One-year changes in insulin and glucose before and after a standardized glucose load.

RESULTS

As compared with controls fasting insulin in pmol L-1 decreased significantly in the combined diet and exercise group (3.9 +/- 6.2 versus -22.6 +/- 4.7 respectively, P = 0.003). Insulin in pmol L-1 after glucose load decreased significantly in all intervention groups compared to controls (diet: -82.2 +/- 49.9 P = 0.02; exercise: -92.4 +/- 60.1 P = 0.03; diet + exercise: -179.6 +/- 46.1 P = 0.0004). Fasting glucose in mmol L-1 decreased significantly in the diet alone group (0.21 +/- 0.07 P = 0.006) and in the diet+exercise group (-0.26 +/- 0.08 P = 0.005). In a subgroup analysis of the good responders, the observed changes with respect to total cholesterol (-0.76 mmol L-1), HDL cholesterol (0.16 mmol L-1), triglycerides (-0.72 mmol L-1), systolic and diastolic blood pressure (-8.5/ -6.8 mmHg) were all statistically significant compared to the control with P < 0.001).

CONCLUSIONS

Exercise and diet intervention and in particular the combination of the two, were effective in improving carbohydrate metabolism. Associated risk factors were also affected in a beneficial direction.