The aim of present study was to assess the effect of dehydration on MAXIMAL FAT OXIDATION ((MFO)) and FATmax. Ten nonathletes male college students(age, 21.3±2.2 yrs; weight, 71.0±8.3 kg; height, 172.5±4.1 cm; BMI, 23±1.3 kg/m2; body FAT, 18.3±4.6%; VO2max, 38.8±4.2 ml/kg/min) performed an incremental exercise test to exhaustion on a treadmill in two separate sessions. In control session they were euhydrated and in dehydration session were dehydrated induced sauna exposure before testing. FAT and CHO OXIDATION were determined using indirect calorimetry during exercise protocol. For each individual, MAXIMAL FAT OXIDATION ((MFO)), the exercise intensity at which (MFO) occurred (FATmax) and crossover point were determined. The result of paired t-test indicated that (MFO) in Dehydration trial was significantly lower than which in Control trial (0.24±0.05 vs. 0.31±0.08 g/min; p£0.05). Also FATmax was significantly lower in Dehydration trial compare with control trial (40.4±8.3 vs. 46±7.8 %VO2max; p 0.05). Crossover point was shifted to lower intensity due to dehydration (44.8±9.2 vs. 53.4±6.7 %VO2max; p£0.05). These findings demonstrated that dehydration is associated with decrease in relative FAT OXIDATION due to increasing CHO OXIDATION during exercise, also induced shift in the FATmax and crossover point to lower exercise intensity. This shift may have been one cause for the decrease in time to exhaustion for the Dehydration trial.

The aim of this study was to comparison of MAXIMAL FAT OXIDATION ((MFO)) rate in non-athletes collegiate men and women. Ten men and 10 women performed an incremental running exercise with 3 min stages on treadmill. During the test, FAT OXIDATION rate was measured by indirect calorimetry method. MAXIMAL FAT OXIDATION ((MFO)) and the exercise intensity at which (MFO) occurred (FATmax) were determined in each subject. Using independent t-test to compared between groups. Absolute FAT OXIDATION rate (g/min) in men was significantly higher than women in all relative exercise intensities (P £0.05). But in relative FAT OXIDATION rate (g/min/kg ffm) no difference was observed between groups. (MFO) in men was significantly higher than women (0.26±0.07 and 0.17±0.05 g/min respectively; P £ 0.05). Nonetheless, (MFO) was occurred in same exercise intensity in men (41.1±7.7 VO2max %) and women (40.2±7.8 VO2max %). CHO OXIDATION rate in men was higher than women in exercise intensities above 40% VO2max and proportion of FAT OXIDATION in exercise energy expenditure has no significant difference between groups. The changes in FAT OXIDATION defined by VO2max and FFM were 56 percent. However, the results of present study shown that men have higher FAT OXIDATION and (MFO) than women but women may be have higher FAT OXIDATION than men if they matched together by fitness and muscular mass.

FAT OXIDATION during exercise can be influenced by exercise intensity and duration, training status, diet and physical activity level. However, few studies have investigated the effect of time of day on the rate of FAT OXIDATION during exercise. Thus the present study was designed to investigate the effect of time of day on indexes of FAT OXIDATION in active young women. For this purpose, 14 healthy women (mean±SD age, BF%, weight, BMI and Vo2max: 21.6±1.6 years, 18.3±4.6 %, 51.2±3.3 kg, 22±1.7 kg/m2, 40.8±4.2 ml/kg. min) voluntarily participated in this study. The exercise test was performed in two separate sessions in the morning (7: 00) and evening (19: 00). There was a 7-day interval between the two tests. The protocol was an incremental exercise to exhaustion on a treadmill. The volunteers started exercising at a speed of 58.3 m/min and at a gradient of 1%.Then, the speed increased to 16.7 m/min every three minutes until 125 m/min. At this point, the gradient increased by 2% per three minutes until RER=1 was achieved. VO2 and VCO2 were measured throughout the exercise by an automated gas analysis system. The data were analyzed using independent t test (a=0.05). The findings of the present study showed that no significant difference in MAXIMAL FAT OXIDATION between morning and evening exercises (morning: 0.39±0.13 vs. evening: 0.44±0.11, P>0.05). There was no significant difference in FAT Max between morning and evening (P>0.05). However, the mean intensity of MAXIMAL FAT OXIDATION was higher in the evening. Finally, it can be concluded that probably time of day (morning and evening) does not have an effect on substrate OXIDATION during intensive exercise.

Nowadays, obesity has become a problem in the developing country and left the government with huge treatment costs. Due to this, researchers have started large scale studies to find the best exercise protocols for FAT loss. Two popular terms in the studies that investigate the effects of exercise training on FAT loss are MAXIMAL FAT OXIDATION ((MFO)) and FATmax (exercise intensity which the maximum FAT OXIDATION is occurred). In this study (MFO), FATmaxand studies which assess the effect of exercise on FAT OXIDATION are reviewed. Although a lot of research has been done to determine FATmax, the data are inconsistent. However, most researchers believe that the highest amount of lipid OXIDATION occurs at low to moderate intensities ranging from 35 to 65% of vo2max.

The aim of present study was to compare FAT OXIDATION rates, MAXIMAL FAT OXIDATION ((MFO)) and the intensity that elicits MAXIMAL FAT OXIDATION (FATmax), in two exercise modes (running and cycling). Ten untrained student girls (aged 23.1±1.90 yr; height 163.3±10 cm; weight 57.3±4.4 kg; body FAT percent 28.2±3.1) participated in this study as subjects. Subjects completed MAXIMAL graded exercise tests on the cycle ergometer and the treadmill. Gas exchange and heart rate were measured 10 min before and throughout the exercise test. FAT OXIDATION rates were calculated using stoichiometric equations. Two way analysis variance for repeated measure, bonferroni, t tests were performed to analysis data. The result of this study showed that FAT OXIDATION rates (0.13±0.03 vs. 0.06±0.02 g/min), (MFO) (0.21±0.06 vs. 0.15±0.05 g/min) and VO2max (28.4±4.5 vs. 23.2±4.4 ml/kg/min) was significantly higher during the treadmill test compared with the cycle ergometer (p£0.05). While, FATmax rates was not significantly difference between exercise modes (%42.83 VO2max on treadmill vs. %47.87 VO2max on ergometer). From the result of this study it can be concluded that FAT OXIDATION rates in similar relative intensity of exercise are remarkably different in mode of exercise. Also, MAXIMAL FAT OXIDATION is higher in activities which used higher muscle mass.