To the best of our knowledge, this is the first study in which direct comparison of the effect of RSO or ASO supplementation on weight loss, and anthropometric and metabolic parameters was performed in a weight loss program in patients with obesity. In contrast to studies based on long-term body mass reduction protocols, we evaluated whether the short-time weight loss program can induce satisfactory anthropometric and metabolic changes in adult patients with obesity.
No significant difference in weight loss or other anthropometric parameters were observed between the analyzed groups. Both oils showed favorable effect on carbohydrate and lipids profiles. However, the beneficial effects of ASO exceeded that of RSO in terms of lipid profile.
At the end of study, significant reduction in weight, BMI, WC, HC, and FM and were observed in the AO, RO, and C groups. The weight loss and improvement in body composition observed in this study is comparable with those observed in other studies [12, 13]. It is noteworthy that the most significant reduction in FM and VFM was observed in patients without oil supplementation, although this did not affect the improvement in metabolic parameters.
After the 3-weeks weight loss program, significant reductions in fasting serum insulin level and HOMA-IR were noted in the AO and RO groups, but not in the C group. Statistically significant reduction in fasting glucose level was observed only in the AO group.
In our study, we observed improvement in TC, non-HDL, TG/HDL, LDL, and TG levels in response to weight loss; however, the changes were significant only in the AO group. In both AO and RO groups, the significant increase in percentage HDL was observed at the end of the study.
The differences observed between the groups in the effectiveness of improving metabolic parameters may be due to the differences in the fatty acid composition of ASO and RSO. ASO contains lower amount of MUFAs (~ 24% vs. ~59%) and LC n-3 PUFAs (~ 1% vs. ~11%) and has poorer PUFA/SFA and USFA/SFA ratio than RSO. Furthermore, ASO was less beneficial as its n-3/n-6 ratio was lower than that of RSO . In contrast, ASO is one of the oils with highest squalene content. Strong anticancer, antioxidant, drug carrier, detoxifier, skin hydrating, and emollient activities of squalene have been reported both in animal models and in vitro environments .
A previous study showed that replacement of usual edible oils with oils rich in unsaturated fatty acids [USFA] such as ASO and RSO resulted in lipid-modulating, anti-atherogenic, antioxidative, anti-inflammatory, hepatoprotective, and hypotensive effects [8–9]. The quality of dietary fat modulated the development of obesity by interacting with genes involved in fatty acid metabolism, adipogenesis, and endocannabinoid system .
Evidence from animal studies suggested that LC n-3 PUFAs may protect against weight gain, raising the possibility that LCn-3 PUFA facilitates weight loss or differential changes in body composition when incorporated into weight-loss programs . Furthermore, Borsonelo et al.  demonstrated anxiolytic-like effect of a diet enriched with PUFAs in an animal model of anxiety. A time-dependent effect of LC n-3 PUFAs on weight loss was also established in humans [19, 20]. Certain studies showed that compared to PUFAs, MUFAs affect weight loss better, as MUFAs induce more energy expenditure, diet-induced thermogenesis, and fat oxidation than PUFA diet [21, 22]. In our study, there were no significant differences in the effectiveness of weight loss between patients in the RO, AO, and C groups. However, weight, BMI, WC, HC, and FM in the AO group tended to decrease more than in the RO group. On the other hand, important changes in FM% and VFM were observed in the C group, although this did not affect the clinical parameters.
Numerous studies have indicated that consumption of high levels of MUFAs and PUFAs improves glucose metabolism and lipid profile compared to consumption of fats containing higher levels of SFAs. However, whether metabolic parameters will improve more when the dietary SFAs are replaced by higher concentrations of MUFAs or of PUFAs is still unclear [23, 24]. The meta-analysis conducted by Qian et al.  provided evidence that compared to consumption of high-PUFA diets, consumption of MUFA-rich diets resulted in significant reduction in fasting plasma glucose and a nonsignificant reduction in fasting insulin, TG, and LDL levels . In contrast, Miller et al.  showed that substitution of SFA with PUFAs in patients with metabolic syndrome was associated with higher reductions in TG and improvement in endothelial function than MUFAs.
Previous studies have suggested that RSO can be used in glucose profile normalization in humans [26–38]. The study conducted in a Canadian academic center on patients with type 2 diabetes treated with an oral antihyperglycemic agent showed that consumption of canola oil-enriched low-GL diet for 3 months improved glycemic control . The effect of ASO on glucose metabolism was less clear. Kim et al.  showed that 3 weeks of ASO supplementation (100 mg/kg) significantly reduced the serum glucose level in streptozocin-induced diabetic rats. The beneficial effect of ASO in patients with diabetes mellitus type 2 has also been confirmed by Miroshnichenko et al. . In this study, improvements in fasting glucose and insulin levels, and insulin sensitivity were also observed in the AO and RO groups, although these changes were higher in subjects supplemented with ASO .
The effect of RSO on circulatory cholesterol level has been observed in most short-term interventions. Lin et al.  showed that diet rich in RSO resulted in substantial reductions in TC (12.2–12.5%) and LDL levels (17%); however, changes in HDL and TG levels with canola oil are inconsistent. Furthermore, previous studies [31–33] have reported that compared to consumption of high-SFA diets, consumption of diet enriched with RSO resulted in 8−10% reduction in HDL concentrations. Our data showed that calorie-restricted RSO-supplemented diet did not significantly affect TC and TG levels. We observed slight increase in HDL concentration and improvement in non-HDL and TG/HDL ratio, although these changes were not statistically significant.
Gonor et al.  investigated the beneficial effect of diet supplemented with squalene (600 ml/d) from amaranth oil (18 ml/d) on TC and TG concentration and composition of fatty acids of erythrocytes in patients with ischemic heart disease and hyper lipoproteinemia. Similarly, Martirosyan et al.  showed that 3 weeks of low-sodium/low-fat diet containing ASO (3, 6, 12, or 18 ml/d) promoted positive dose-dependent changes in the serum TC, LDL, and TG levels among obese patients with coronary heart disease and hypertension. In our study, we observed that 3-week intervention with ASO supplementation (20 ml/d) lead to significant reduction in TC, %HDL, LDL, and TG levels and slight non-significant increase in HDL level. Statistically significant improvement in the non-HDL and TG/HDL levels were also observed in the AO group. Although, ASO contains lower amounts of MUFA and LC n-3 PUFA than RSO, our study demonstrated that ASO is more effective in improving lipid profiles than RSO. Although further investigations are required for understanding the underlying reason for this observation, our results suggest that incorporation of moderate amounts of dietary squalene in a weight loss program that includes consumption of an equivalent amount of high MUFA and LC n-3 PUFA oils improves the metabolic profile of obese patients.
The major limitations of this trial are the small sample size and relatively short time of intervention. The main reason for this was the inability to interrupt professional and family duties for 3 weeks. However, it is noteworthy that this is one of the few studies conducted under specific and strictly controlled conditions, which is rare in nutritional interventions. Patients who participated in the study received the same type of hypocaloric diet prepared by the dietetic food catering and underwent the same physical activity program with the physical therapist. The 3-week hospitalization of the study population allowed control of their involvement in the intervention. Although dual energy X-ray absorptiometry (DXA) is the gold standard for the assessment of body composition, the bioimpedance method (BIA) was used in the study due to non-invasiveness, lower cost, and widespread use.