Exercise Training at Maximal Fat Oxidation Intensity for Overweight or Obese Older Women: A Randomized Study.

Author:Cao, Liquan
 
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Introduction

Worldwide prevalence of overweight and obesity has been epidemic (Ng et al., 2014; Stein and Colditz, 2004). Obesity prevalence has increased in all age groups, in particular, the 2015 global data showed that nearly 20% of older women aged 60-64 years were obese, while the obesity rate for men of the same age group was about 10% (Chooi et al., 2019). Obesity amongst older adults may cause the development of type 2 diabetes, cardiovascular disease, Alzheimer's disease, osteoarthritis and other diseases (Cetin and Nase, 2014; Osher and Stern, 2009). Among the different interventions, aerobic exercise training has been recognized as an effective means of prevention and treatment for overweight and obesity (Donnelly et al., 2009; Jakicic and Otto, 2005). Previous aerobic exercise training studies in older people with overweight and obesity have typically designed the exercise intensity at 50% to 85% of the heart rate reserve (Christ et al., 2004; Ortmeyer et al., 2017; Ryan et al., 2006) or at 40% to 80% of maximal oxygen uptake (V[O.sub.2]max) (Slentz et al., 2004; Solomon et al., 2008). In practice, this intensity range is too broad to determine a precise exercise intensity for an individual. Furthermore, there is little evidence in the literature justifying the exercise intensities mentioned above and which energy substrates were used at those intensities. Therefore, designing and evaluating an individualized aerobic exercise training program on the basis of the pattern of energy substrate utilization for treating or preventing overweight and obesity in older people remains a critical task for exercise scientists.

During graded exercise tests, studies of energy substrate utilization have indicated that fat oxidation rate increases with a gradual increase in exercise intensity. This oxidation rate reaches a peak at a certain intensity and then begins to decrease (Brooks and Mercier, 1994; Hultman, 1995). The exercise intensity at which the peak fat oxidation is observed is defined as the maximal fat oxidation rate (FATmax) (Jeukendrup and Achten, 2001). FATmax is a low-to-moderate exercise intensity. Our team has reported that overweight middle-aged women (51 [+ or -] 6 years) reached their FATmax at 52% V[O.sub.2]max (Tan et al., 2016). Some researchers have applied the FATmax exercise training to adults with metabolic diseases (Botero et al., 2014; Dumortier et al., 2003; Lanzi et al., 2015; Tan et al., 2018; Tan et al., 2016; Tan et al., 2012; Venables and Jeukendrup, 2008). The main outcomes have included decreased body fat (Tan et al., 2016) or improved ability to oxidise lipids during exercise (Dumortier et al., 2003) in middle-aged overweight or obese individuals. Our team also reported that FATmax exercise training can promote glucose metabolism and adipokines regulation in older women with type 2 diabetes (Tan et al., 2018). However, to date there have been no studies that have applied FATmax exercise training in older women who are overweight or obese. FATmax is a low-to-moderate exercise intensity and with a higher fat oxidation rate than other aerobic exercise intensities. Hence, it is logical to expect FATmax would be a suitable exercise intensity for overweight or obese older people who want to decrease their body fat, as well as improve functional capacity. Therefore, the purpose of the present study was to investigate the effects of FATmax exercise training on body composition, lipid profile, cardiovascular function, muscle strength, and body flexibility in older women with overweight or obesity. We hypothesized that FATmax training would improve the measured variables in the trained participants, compared to the non-exercise (control) participants.

Methods

Participants

Thirty overweight or obese women, aged 60-69 years with body mass index (BMI) > 25kg/[m.sup.2], were recruited via local medical practitioners. None of them had been engaged in regular exercise training over the past two years. Individuals with heart disease, resting blood pressure (BP) greater than 160/95 mmHg, type 2 diabetes, pulmonary diseases, impaired renal or liver function, or who were unable to participate in the exercise training protocol due to orthopedic or neurological limitations were excluded. Before the baseline tests, the exact details of the study were explained to the participants and a written informed consent to the study was obtained from each of them. All methods and procedures of the present study were approved by the Ethics Committee of Tianjin University of Sport, China.

Study design

Participants were randomly allocated into the Exercise or Control groups, 15 in each group. A third party not involved in the present study listed participants in alphabetical order, according to their family name. Odd numbered participants were allocated to the Exercise group and even numbered participants were allocated to the Control group. After the baseline tests, which measured body composition, FATmax rate, predicted V[O.sub.2]max, lipid profile, cardiovascular variables, hand grip strength, and body flexibility, the Exercise group took part in supervised exercise training at the individualized FATmax intensity for 12 weeks. The Control participants maintained their individual habit of physical activity and did not engage in any prescribed exercise training during the interventions. All variables in the baseline tests were measured again at the end of the experiments. The post-intervention tests were performed at least 48 hours after the last training session of the Exercise group. Under full supervision, all exercise tests and training sessions were conducted in the Exercise Physiology Laboratory and sports grounds of Tianjin University of Sport. There were no diet interventions introduced during the experimental period for either group of participants.

Measurements

Body mass and height of each participant were measured to calculate their BMI by dividing body mass (kg) by height in meters squared ([m.sup.2]). The waist circumference (WC) was measured at the level of the umbilicus horizontally. After an overnight fast, body composition was measured using a dual-energy X-ray absorptiometry (DXA) (Prodigy Advance, GE Healthcare Lunar, USA). Using the computer program for soft tissue analysis provided by the manufacturer, the total body fat (%) was determined. Fat mass and fat-free mass were calculated. An experienced technician completed all measurements. To assess abdominal obesity, the visceral trunk fat percentage (% in area) was estimated by bioelectrical impedance analysis equipment (Body Composition Analyser Tanita AB-140 Viscan, Tanita Corporation of America, Inc., USA).

FATmax of each participant of the Exercise group was measured at baseline only. Participants refrained from...

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