Fat Oxidation, Hormonal and Plasma Metabolite Kinetics during a Submaximal Incremental Test in Lean and Obese Adults

Abstract

This study aimed to compare fat oxidation, hormonal and plasma metabolite kinetics during exercise in lean (L) and obese (O) men. Sixteen L and 16 O men [Body Mass Index (BMI): 22.9±0.3 and 39.0±1.4 kg.m−2] performed a submaximal incremental test (Incr) on a cycle-ergometer. Fat oxidation rates (FORs) were determined using indirect calorimetry. A sinusoidal model, including 3 independent variables (dilatation, symmetry, translation), was used to describe fat oxidation kinetics and determine the intensity (Fatmax) eliciting maximal fat oxidation. Blood samples were drawn for the hormonal and plasma metabolite determination at each step of Incr. FORs (mg.FFM−1.min−1) were significantly higher from 20 to 30% of peak oxygen uptake () in O than in L and from 65 to 85% in L than in O (p≤0.05). FORs were similar in O and in L from 35 to 60% . Fatmax was 17% significantly lower in O than in L (p<0.01). Fat oxidation kinetics were characterized by similar translation, significantly lower dilatation and left-shift symmetry in O compared with L (p<0.05). During whole exercise, a blunted lipolysis was found in O [lower glycerol/fat mass (FM) in O than in L (p≤0.001)], likely associated with higher insulin concentrations in O than in L (p<0.01). Non-esterified fatty acids (NEFA) were significantly higher in O compared with L (p<0.05). Despite the blunted lipolysis, O presented higher NEFA availability, likely due to larger amounts of FM. Therefore, a lower Fatmax, a left-shifted and less dilated curve and a lower reliance on fat oxidation at high exercise intensities suggest that the difference in the fat oxidation kinetics is likely linked to impaired muscular capacity to oxidize NEFA in O. These results may have important implications for the appropriate exercise intensity prescription in training programs designed to optimize fat oxidation in O.

Short‐term HIIT and Fatmax training increase aerobic and metabolic fitness in men with class II and III obesity

“…After the intervention, FORs during exercise were higher and whole‐body fat oxidation kinetics were characterized by a greater dilatation and right‐shift translation in both groups. We recently showed that men with obesity and severe obesity presented a lower Fat max and reliance on fat oxidation compared to their lean counterparts . These findings demonstrated that only 2 weeks of training may increase Fat max and FORs, which suggests that fat oxidation may rapidly improve in this population.…”

¿Puede el ejercicio físico per se disminuir el peso corporal en sujetos con sobrepeso/obesidad?

“…rc: restricción calórica; eF: entrenamiento físico; kg: kilogramos. máxima oxidación de grasas (MOG) en sujetos sanos no entrenados se encuentra entre 60 y 65% del VO 2máx 39 , pero en pacientes con sobrepeso/obesidad este valor tiende a estar reducido a 45-50% 40 . También se ha observado que la MOG ocurre a una misma intensidad cuando se compara entre cinta rodante y cicloergómetro, pero la tasa de oxidación de grasas (e.g., gramos × minuto -1 ) es mayor en cinta rodante 41 .…”

“…esquema resumen de factores relacionados con la intensidad del ejercicio, la utilización de sustratos por el musculo esquelético y la percepción subjetiva del esfuerzo en sujetos obesos y entrenados (datos no publicados de nuestro laboratorio, de Achten y Jeukendrup 42 , Jeukendrup y Achten 75 y lanzi y col. 40,76 ). MoG: intensidad a la cual ocurre la máxima oxidación de grasas;…”

Vascular Dynamics and Peripheral Oxygen Uptake in Obese Individuals during Progressive Physical Exercise

“…Based on previous experience [22], peak O 2 uptake (V • O 2peak ) and peak power output (PPO) were measured using a maximal ramp incremental test performed to exhaustion on a cycle ergometer (Ebike Basic BPlus, Niskayuna, NY, USA). After a 3-min rest period, the L group began with a 5-min warmup at 60 W (40 W for the O group), followed by a linear increase in PPO (by 30 W;…”

“…Thereafter, subjects performed a submaximal incremental test. After a standardized 10-min warmup at 20% PPO, the PO was increased by 7.5% PPO every 6 min (until 57.5% PPO or until the respiratory exchange ratio reached 1.0) as previously described [22].…”