Aerobic exercise but not resistance exercise reduces intrahepatic lipid content and visceral fat and improves insulin sensitivity in obese adolescent girls: a randomized controlled trial

Abstract

Lee S, Deldin AR, White D, Kim Y, Libman I, Rivera-Vega M, Kuk JL, Sandoval S, Boesch C, Arslanian S. Aerobic exercise but not resistance exercise reduces intrahepatic lipid content and visceral fat and improves insulin sensitivity in obese adolescent girls: a randomized controlled trial. Am J Physiol Endocrinol Metab 305: E1222-E1229, 2013. First published September 17, 2013; doi:10.1152/ajpendo.00285.2013.-It is unclear whether regular exercise alone (no caloric restriction) is a useful strategy to reduce adiposity and obesity-related metabolic risk factors in obese girls. We examined the effects of aerobic (AE) vs. resistance exercise (RE) alone on visceral adipose tissue (VAT), intrahepatic lipid, and insulin sensitivity in obese girls. Forty-four obese adolescent girls (BMI Ն95th percentile, 12-18 yr) with abdominal obesity (waist circumference 106.5 Ϯ 11.1 cm) were randomized to 3 mo of 180 min/wk AE (n ϭ 16) or RE (n ϭ 16) or a nonexercising control group (n ϭ 12). Total fat and VAT were assessed by MRI and intrahepatic lipid by proton magnetic resonance spectroscopy. Intermuscular AT (IMAT) was measured by CT. Insulin sensitivity was evaluated by a 3-h hyperinsulinemic (80 mU·m 2 ·min Ϫ1 ) euglycemic clamp. Compared with controls (0.13 Ϯ 1.10 kg), body weight did not change (P Ͼ 0.1) in the AE (Ϫ1.31 Ϯ 1.43 kg) and RE (Ϫ0.31 Ϯ 1.38 kg) groups. Despite the absence of weight loss, total body fat (%) and IMAT decreased (P Ͻ 0.05) in both exercise groups compared with control. Compared with control, significant (P Ͻ 0.05) reductions in VAT (⌬Ϫ15.68 Ϯ 7.64 cm 2 ) and intrahepatic lipid (⌬Ϫ1.70 Ϯ 0.74%) and improvement in insulin sensitivity (⌬0.92 Ϯ 0.27 mg·kg Ϫ1 ·min Ϫ1 per U/ml) were observed in the AE group but not the RE group. Improvements in insulin sensitivity in the AE group were associated with the reductions in total AT mass (r ϭ Ϫ0.65, P ϭ 0.02). In obese adolescent girls, AE but not RE is effective in reducing liver fat and visceral adiposity and improving insulin sensitivity independent of weight loss or calorie restriction. insulin sensitivity; intrahepatic lipid; visceral fat; exercise; adolescents THE EPIDEMIC RATE OF CHILDHOOD OBESITY is a major health concern in the US, as overweight and obese youth are at increased risk of developing comorbidities such as nonalcoholic fatty liver disease (35), type 2 diabetes (33), and metabolic syndrome (21, 41), once considered diseases of adulthood. Although both diet and physical activity are considered to be the first lines of approach to treat obese youth (9), we recently reported that, in obese adolescent boys, increasing physical activity alone, independent of calorie restriction, is beneficial to reduce total fat, visceral adiposity, and intrahepatic lipid and improves cardiorespiratory fitness (CRF) (22). In obese adolescent girls, the utility of exercise alone as a strategy for reducing obesity-related metabolic risk factors is currently unclear. Given the lower physical activity levels in girls than in boys (14) and the fact that physical activi...

Waist circumference is associated with liver fat in black and white adolescents

“…1 H-MRS was performed with a 3.0 Tesla MR system (Siemens, Tim Trio, Erlangen, Germany) using a body matrix coil and a spine matrix (Siemens) using our established protocol described elsewhere (Lee et al 2012;Lee et al 2013). Fatty liver was defined as liver fat [(methylene lipid peak/methylene lipid peak + water peak) × 100] ≥ 5.0% as shown previously (Perseghin et al 2006).…”

Exercise Training Improved Body Composition, Cardiovascular Function, and Physical Fitness of 5-Year-Old Children With Obesity or Normal Body Mass

“…Thus, exercise training has been applied as the first choice for children who are overweight or obese, but not morbidly obese caused by underlying pathologies (16). Previous studies have reported that exercise training in children with obesity improves their body composition (10,28), cardiovascular function (4,7), and physical fitness (12,13,29). However, there are few studies of the effects of exercise training in obese children aged 5 years.…”

The benefits of exercise for patients with non-alcoholic fatty liver disease

“…Moreover, despite performing double the training load of the aerobic alone or PRT alone groups, aerobic exercise combined with PRT led to a non-significant reduction in liver fat. A superior hepatic benefit of aerobic exercise training was also demonstrated in obese adolescent girls [12]; however, comparable reductions between aerobic and resistance training have been observed in NAFLD patients with type 2 diabetes [5] and in obese adolescent boys [13].…”

“…With respect to aerobic exercise, these guidelines promote moderate-intensity cardiorespiratory exercise training for ‡30 min on at least 5 days per week, or vigorous cardiorespiratory exercise training for ‡20 min on 3 days per week, or a combination of both and align with global recommendations for health, fitness and disease prevention [10]. Exercise interventions meeting these guidelines consistently demonstrate reduction in liver fat of 10-43% in patients with NAFLD [5,6,[11][12][13][14][15][16].…”

“…To date, there is sparse evidence for the efficacy of PRT as per these guidelines for liver fat reduction. Of the nine studies employing PRT in isolation, five observed a significant reduction in liver fat [5,13,[17][18][19], three of which conformed with the abovementioned guidelines [5,13,18], while four showed no benefit [12,[20][21][22] with discrepancies in outcomes likely due to the large heterogeneity in study design. These differences include the use of circuit-based training (which has a concurrent 'aerobic' exercise stimulus) [19,22], the use of home-based prescription [17], and variation in training intensities and study populations, all of which combined limit the ability to generalize findings and draw practical conclusions.…”