A high percentage of CV risk factors, particularly high LDL-C levels and low levels of physical activity and aerobic fitness was observed in this group of young healthy participants. As expected, overweight (body fat≥20%) had higher body weight, BMI, circumference measurements and a greater number of CV risk factors than lean participants (body fat <20%). Most of the parameters assessed were similar between overweight and lean participants except for higher EI/BW, EE/BMI, PAEE/BW ratios and VO2max in the lean compared to overweight participants using either %body fat or %body fat/m2 to classify the study participants into adiposity levels. Levels of HDL-C were higher in the lean compared to overweight participants using %body fat to classify participants into adiposity levels but the difference was no longer significant when %body fat/m2 was used. Having multiple CV risk factors was more common among those with higher body fatness and lower dietary MUFA intake.
Almost 70% of the participants had high levels of LDL-C and almost half had low levels of cardio respiratory fitness. Aerobic fitness is an important independent predictor of CV disease in middle-aged men. Whereas a lower level of fitness has been associated with a 4.7-fold increased risk of myocardial infarction and stroke , moderate fitness seems to protect against the influence of other predictors of mortality in adults [33–35]. Other strong independent risk factors for CV disease include high percentage of body fat  and high WC [37, 38]. Using 88 cm as a cut-point for WC, 29% of the participants in this study had high WC.
Results in the current study are consistent with published data from other studies with young men for body fat [39, 40], RMR [41–44], EE [41, 42], PAL [41, 42], BP [45–48], VO2max[39, 49], BMI and circumference measurements . BMI is often used to classify subjects in relation to degree of obesity. However this index has limitations as it does not account for variation in body fat distribution and abdominal fat mass . The misclassification of normal and overweight participants using BMI found in the current study is consistent with a previous study . Participants in the current study had better blood lipid profiles including lower TC, LDL-C and TG and higher HDL-C values compared to other studies examining young men [52–54].
Most of the participants in the current study had one or two CV risk factors. Similar findings have been observed in other studies [55, 56]. Populations with multiple behavioral risk factors are at greatest risk for chronic disease and premature death compared with people with single or no risk factors [12, 57] whereas participants with CV disease were more likely to have three or more CV risk factors (32%) than those without CV diseases (9.5%) . The higher levels of risk factors at younger ages in men compared to women leads to CV disease presenting 10 years later in women .
The prevalence of CV disease has been shown to increase not only with increased number of behavioral risk factors but also with age and obesity level . In addition, obesity was positively associated with the risk of premature death from endogenous causes in populations as young as children supporting the view that childhood obesity is a marker of early metabolic derangement, whereas most of the other risk factors evolve later . Moreover obesity is frequently associated with less favorable biochemical indicators as found in the current study. Lean men in the current study had more favourable biochemical indicators than overweight men. Systolic BP has previously been related to percent body fat [36, 61] and obesity, while abdominal obesity and visceral fat have been positively associated with higher TC , LDL-C [7, 8] and TG [8, 62] and negatively associated with HDL-C [62, 63]. It has been proposed that the mechanism of the link between increased abdominal fat and risk factors for CV disease is related to higher plasma levels of free fatty acids originating from the enlarged abdominal fat depots . Plasma LDLs cross the vascular endothelium, enter the subendothelial space, become modified and accumulate in the macrophages, which are converted into foam cells that progress to form the atherosclerotic plaque . HDL-C may minimize the accumulation of foam cells in the artery wall and inhibit the oxidative modification of LDL-C .
Overweight people have been reported to have higher RMR than lean individuals [65–68]. However, overweight and lean men classified by using either % body fat or %body fat/m2 in the current study had similar RMR, possibly due to similar amount of FFM which can contribute up to 80% of the RMR .
In the current study, the mean EI, EE and PAEE were similar in both groups and similar to other studies [70, 71]. When EI was divided by body weight, the finding of a lower EI per weight observed in overweight men compared to lean men is consistent with other reports . Higher self-reported EI compared to higher self-reported EE for both lean and overweight men suggests underreporting of EI and/or over-reporting of EE which is consistent with other studies [72–74]. This reflects ‘the halo effect’ , where behaviours perceived as ‘good’ will be over-reported (such as doing physical activity), and those perceived as ‘bad’ underreported (such as consuming dietary fat). Also consistent with other studies [66–68], that when EE was divided by BMI and PAEE was divided by BW, these ratios were higher in lean compared to overweight men suggesting that the increased energy cost of moving a larger body mass may have contributed to overweight men expending similar amount of energy compared to lean men.
Lean men in the current study had a higher mean VO2max than the overweight men. Increased VO2max has been associated with increased cardio respiratory fitness. The association between reduced cardio respiratory fitness and increased body fat observed in overweight participants in the current study has been reported in other studies [75–77].
The most striking finding of the current study was that participants consuming a diet in which MUFA contributed a high percentage of EI (>12% of the EI) had an average smaller number of CV disease risk factors compared to those consuming diet in which MUFA contributed to low percentage of EI (<12% of the EI). Dietary MUFA have been found to promote a healthy blood lipid profile, mediate blood pressure, and favorably modulate insulin sensitivity and glycemic control . A reduced predicted coronary heart disease risk by 6.37% was observed in diabetic men consuming a moderately high fat diet (30-50% of EI) in which MUFA accounted for 23% of EI compared to diabetic men consuming a low-fat diet (18-30% of EI) in which MUFA accounted for only 11.4% of the total EI . A systematic review  found that dietary MUFA were associated with a 20% reduced risk in coronary heart disease events.
The findings of the current study show that intake of MUFA favorably affects CV risk factors regardless of the source. Favorable effects on blood lipids were found in participants of a randomized parallel controlled-feeding trial undertaken by Bos et al.  consuming MUFA predominantly from either plant or animal sources. After a two week run-in diet high in saturated fat, participants were allocated to a high MUFA diet primarily from animal sources, a Mediterranean diet in which MUFA were primarily from plant sources, or the high saturated diet for eight weeks. Participants consuming a high MUFA diet predominantly from animal foods had reduced TC and LDL-C whereas participants consuming a high MUFA diet predominantly from plant foods had increased HDL-C and reduced ratio of TC/HDL-C .
Use of body fat estimated by DEXA rather than use of BMI to classify the participants into each group was an advantage of the current study. DEXA is the only widely available technology capable of providing regional measures of fat and lean mass, separating body mass into fat and lean components, thereby permitting the evaluation of fat mass without the confounding influence of other tissue constituents . In addition, it has been shown that fat and lean distribution may predict health outcomes . Studies have shown that lean mass and weight scale with height to approximately the power of two, establishing an analytic framework for height-scaled inces. The use of %body fat/m2 has been proposed to classify adiposity levels. However it is not known whether or not the use of the proposed %body fat/m2 classification scheme will confer benefits over BMI in terms of predicting obesity-related morbidity or mortality. The %body fat/m2 classifications were based on prevalence data, not disease risk, and therefore the clinical utility of the %body fat/m2 classification scheme will not be known until data relating disease risk to %body fat/m2 becomes available . For these reasons we have used both %body fat and %body fat/m2 in order to classify participants of the current study and have showed that there was no difference in the findings using either %body fat or %body fat/m2 to classify the study participants into groups.
A small sample size was a limitation of the current study. Another limitation is that RMR of half of the participants was assessed using different equipment due to technical problems. However the likelihood of measurement bias is small because a similar proportion of lean and overweight participants was assessed using each of the equipments. Nevertheless, the results contribute valuable data from a comprehensive clinical assessment of CV risk in young Australian men, an important group which has been under-represented in previous work.
Further studies investigating the effect of MUFA consumption including food sources in CV risk factors in a large sample of broader age range, ethnicity and both genders, are warranted.