Body Composition, Fasting Blood Glucose and Lipidemic Indices Are Not Primarily Determined by the Nutritional Intake of Middle-Aged Endurance Trained Men—Another “Athletes’ Paradox”?

Abstract

Systematic, regular high-volume endurance training induces significant metabolic adaptations in glucose and lipids metabolism, which seems to affect the negative impact of unhealthy nutrition, at least in animal models. The present study aimed to investigate the main determinants of body composition, blood glucose and lipids concentrations between middle-aged sedentary individuals (Sed) and well-trained endurance athletes (Run), both following an unhealthy high-fat diet. In thirty-five Sed (Age: 54.0 ± 6.6 yrs, Body Mass: 77.1 ± 10.5 kg, BMI: 31.3 ± 6.0 kg·m−2) and thirty-six Run (Age: 51.6 ± 5.2 yrs, Body Mass: 85.8 ± 3.4 kg, BMI: 23.2 ± 1.8 kg·m−2), body composition, nutritional intake, energy expenditure, resting metabolic rate (RMR), respiratory exchange ratio (RER), and blood glucose and lipids concentrations were evaluated. Multiple linear regression analyses revealed that body composition, blood glucose and lipids’ concentrations in the Run group were primarily determined by the energy expenditure (B: −0.879 to −1.254), while in the Sed group, by their energy intake (B:−0.754 to 0.724). In conclusion, it seems that in well-trained endurance middle-aged athletes, body composition, blood glucose, and lipids concentrations seem to be determined by their training-induced daily energy expenditure and not by their nutritional intake per se. At the same time, nutrition is the primary determinant in aged-matched sedentary individuals, even if they both follow high-fat diets.

Metabolic Flexibility and Inflexibility: Pathology Underlying Metabolism Dysfunction

“…Both of these studies emphasize the importance of exercise for metabolic health across the lifespan, which is echoed in recent studies examining the role exercise has in metabolic-related chronic diseases [ 12 , 13 , 14 , 15 ]. A recent review highlighted the importance of resistance training for improving outcomes in the early and late stages of frailty and sarcopenia [ 15 ].…”

“…For example, in females across the lifespan (ages 20–60 years), a combination of aerobic and resistance training improved risk factors of metabolic syndrome, including waist circumference, fasting blood glucose, blood pressure, and blood lipid parameters [ 12 ]. Additionally, Methenitis et al examined differences in body composition, blood glucose, and lipid concentrations in sedentary compared to endurance-trained middle-aged adults consuming a high-fat diet [ 14 ]. This study found that training-induced energy expenditure is the main determinant of these metabolic parameters, as well as positive metabolic adaptations that were more influenced by exercise training rather than nutritional intake.…”

“…This study found that training-induced energy expenditure is the main determinant of these metabolic parameters, as well as positive metabolic adaptations that were more influenced by exercise training rather than nutritional intake. The authors theorized that the training volume resulted in improved mitochondrial density and oxidative capacity, leading to improved regulation of CHO and fat metabolism, thus making endurance-trained individuals more metabolically flexible than sedentary individuals [ 14 ]. Similarly, a study assessing functional fitness abilities in individuals with and without metabolic syndrome reported that the fitness level was lower in those with metabolic syndrome, independent of sex and age [ 13 ], and individuals with type 2 diabetes and coronary artery disease had low aerobic exercise capacity [ 16 ], further supporting the idea that exercise may be an important driver of improving metabolic flexibility.…”