The main objective of this research was to determine the effects of a long-term ketogenic diet, rich in polyunsaturated fatty acids, on aerobic performance and exercise metabolism in off-road cyclists. Additionally, the effects of this diet on body mass and body composition were evaluated, as well as those that occurred in the lipid and lipoprotein profiles due to the dietary intervention. The research material included eight male subjects, aged 28.3 ± 3.9 years, with at least five years of training experience that competed in off-road cycling. Each cyclist performed a continuous exercise protocol on a cycloergometer with varied intensity, after a mixed and ketogenic diet in a crossover design. The ketogenic diet stimulated favorable changes in body mass and body composition, as well as in the lipid and lipoprotein profiles. Important findings of the present study include a significant increase in the relative values of maximal oxygen uptake (VO2max) and oxygen uptake at lactate threshold (VO2 LT) after the ketogenic diet, which can be explained by reductions in body mass and fat mass and/or the greater oxygen uptake necessary to obtain the same energy yield as on a mixed diet, due to increased fat oxidation or by enhanced sympathetic activation. The max work load and the work load at lactate threshold were significantly higher after the mixed diet. The values of the respiratory exchange ratio (RER) were significantly lower at rest and during particular stages of the exercise protocol following the ketogenic diet. The heart rate (HR) and oxygen uptake were significantly higher at rest and during the first three stages of exercise after the ketogenic diet, while the reverse was true during the last stage of the exercise protocol conducted with maximal intensity. Creatine kinase (CK) and lactate dehydrogenase (LDH) activity were significantly lower at rest and during particular stages of the 105-min exercise protocol following the low carbohydrate ketogenic diet. The alterations in insulin and cortisol concentrations due to the dietary intervention confirm the concept that the glucostatic mechanism controls the hormonal and metabolic responses to exercise.

There is no clear evidence that vitamin D effectively improves physical capacity in high-level athletes. The aim of this study was to confirm that vitamin D supplementation of soccer players during eight-week high-intensity training would have a significant effect on their aerobic capacity. The subjects were divided into two groups: the experimental one that was supplemented with vitamin D (SG, n = 20), and the placebo group (PG, n = 16), not supplemented with vitamin D. All the players were subjected to the same soccer training described as High-Intensity Interval Training (HIIT). The data of the vitamin D level, PWC170, lactate threshold (LT) were collected just before and after the intervention. A significant increase in vitamin D concentration (119%) was observed in the supplemented group, while the non-supplemented group showed a decrease of 8.4%. The studied subjects improved VO2max results by 20% in the SG, and by 13% in the PG. The improvement in velocity at the LT was similar in both groups. Results of this study show that vitamin D can have a positive, though moderate, effect on aerobic performance in players subjected to high-intensity training in the form of small-sided games for 8 weeks.

Recently, low carbohydrate diets have become very popular due to their numerous health benefits. Unfortunately, little is known about their chronic effects on the blood lipid profile and other cardiovascular disease risk factors in athletic populations. We compared the results of a four week, well-planned low carbohydrate diet (LCD) followed by seven days of carbohydrate loading (Carbo-L) on fasting lipids - triacylglycerol’s (TAG), LDL-C, HDL-C, total cholesterol (TCh), glucose, insulin and HOMA-IR levels in 11 competitive basketball players. During the experiment, we also measured body mass (BM) and body composition changes: body fat (BF), % of body fat (PBF), and fat free mass (FFM). Both diet procedures significantly changed the fasting serum concentration of TAG (p < 0.05) and body fat content (kg and %) (p < 0.05), without negative changes in FFM. The Carbo-L procedure increased (p < 0.05) fasting glucose levels significantly. A LCD may be suggested for athletes who want to reduce body mass and fat content without compromising muscle mass. Several weeks on a LCD does not change the lipoprotein - LDL-C and HDL-C level significantly, while a seven-day Carb-L procedure may increase body fat content and fasting glucose concentration. Such dietary procedures are recommended for team sport athletes to reduce fat mass, lipid profile disorders and insulin resistance.

Objective: The aim of the study was to compare the impact of 6 weeks of reducing daily caloric intake by 20% of total daily energy expenditure (TDEE)-CRI vs. reducing daily caloric intake by 30% of TDEE-CRII on body mass reduction and insulin metabolism in former athletes. Methods: 94 males aged 35.7 ± 5.3 years, height 180.5 ± 4.1 cm, and body mass 96.82 ± 6.2 kg were randomly assigned to the CRI (n = 49) or CRII (n = 45) group. Thirty-one participants (18 subjects from CRI and 13 from CRII) resigned from the study. The effects of both diets on the body composition variables (body mass—BM; body fat—BF; fat free mass—FFM; muscle mass—MM; total body water—TBW), lipid profile (total lipids—TL; total cholesterol—TCh; HDL cholesterol—HDL; LDL cholesterol—LDL; triglycerides—TG), and glucose control variables (glucose—GL, insulin—I, HOMA-IR, insulin-like growth factor-1—IGF-1, leptin and adiponectin) were measured. Results: After adhering to the CR I diet, significant differences were observed in FFM, MM and TG. After adhering to the CR II diet, significant differences were registered in tCh, TL and LDL. Both diets had a significant influence on leptin and adiponectin concentrations. Significant differences in FFM, MM, and tCh were observed between the CR I and CR II groups. At the end of the dietary intervention, significant differences in BF, FFM, MM and TBW were observed between the CR I and CR II groups. Conclusion: The 6 weeks of CR II diet appeared to be more effective in reducing BF and lipid profile and proved to be especially suitable for subjects with high body fat content and an elevated level of lipoproteins and cholesterol. Both reductive diets were effective in improving the levels of leptin and adiponectin in obese former athletes.

The aim of the study was to investigate the efficacy of 6 week Mediterranean diet or 30% calorie restriction on the fatty acid profile and eicosanoids (hydroxyoctadecadienoi acids and hydroxyeicosatetraenoic acids) concentration. Furthermore, basic biochemical variables such as insulin, glucose, HOMA-IR, and a lipid profile were estimated. The study enrolled 94 Caucasian former athletes aged 20-42, with body height of 179 ± 16.00 cm and body mass of 89.26 ± 13.25 kg who had not been active for at least 5 years. The subjects were randomly assigned to one of the three intervention groups: CR group – the 30% calorie restriction (n = 32), MD group - the Mediterranean diet (n = 34), and C group - a control group (n = 28). The pattern of nutrition was analysed before and after the experiment using the 72 h food diaries. In order to evaluate the effect of diet intervention, the following variables were measured: anthropometrics, basic biochemical variables (insulin, fasting glucose, HOMA-IR, lipid profile), fatty acids and their blood derivatives profiles. The CR group showed significantly lower levels of several biochemical variables, i.e., BMI, total cholesterol LDL, TG, total lipids, insulin and HOMA – IR (p < 0.05). Subjects consuming the MD diet significantly decreased their BMI and reduced the level of total lipids (p < 0.05). We did not find any significant changes in the C group. The analysis of the fatty acid profile revealed that the CR group had a significantly decreased EPA level (p < 0.05). The MD group showed a significantly increased level of the DHA (p < 0.05) and improvement in the omega - 3 index (p < 0.05). Subjects following the MD also showed significantly lower concentrations of 15 - hydroxyicosatetraenoic acid (15-HETE). We did not observe any significant differences between the CR and C groups. Within short time, calorie restriction helps to improve lipid variables and insulin resistance. The MD diet seems to be more advantageous in the decrease of inflammation, but does not improve basic biochemical variables. We can conclude that calorie restriction can be a good choice for former athletes, although EPA and DHA supplementation is needed.