High-intensity interval training without weight loss improves exercise but not basal or insulin-induced metabolism in overweight/obese African American women

Abstract

The purpose of this randomized controlled clinical trial was to determine the effect of a 14-week high-intensity interval training (HIIT) intervention with weight stability on metabolic flexibility, insulin sensitivity, and cardiorespiratory fitness in sedentary, premenopausal, nondiabetic, overweight/obese African American women. Twenty-eight subjects were allocated to one of two groups: HIIT, which performed three sessions per week of four high-intensity cycling intervals, or a control group (CON), which maintained their normal level of physical activity. Diet was controlled for all subjects to ensure weight stability. Pre- and postintervention (pre/post), subjects completed an incremental cycling test to limit of tolerance and, following a 10-day high-fat controlled feeding period, a euglycemic-hyperinsulinemic clamp to determine insulin sensitivity and substrate oxidation. Nine members of HIIT (age, 29 ± 4 yr; body mass, 90.1 ± 13.8 kg) and eleven members of CON (age, 30 ± 7 yr; body mass, 85.5 ± 10.7 kg) completed the study. HIIT experienced an increased limit of tolerance (post, 1,124 ± 202 s; pre, 987 ± 146 s; P < 0.05), gas exchange threshold (post, 1.29 ± 0.34 liters/min; pre, 0.97 ± 0.23 liters/min; P < 0.05), and fat oxidation at the same absolute submaximal work rate compared with CON (P < 0.05 for group-by-time interaction in all cases). However, changes in peak oxygen consumption (V̇o2peak), insulin sensitivity, free fatty acid suppression during insulin stimulation, and metabolic flexibility were not different in HIIT compared with CON. High-intensity interval training with weight stability increased exercise fat oxidation and tolerance in subjects at risk for diabetic progression, but did not improve insulin sensitivity or fat oxidation in the postabsorptive or insulin-stimulated state.

High‐intensity interval training improves insulin sensitivity in older individuals

“…The HIT‐induced improvement in insulin sensitivity shown in the present study was not gender specific, which supports the findings of Robinson et al and Richards et al Contrastingly, Metcalfe et al showed an improvement in insulin sensitivity (Cederholm index) in males only, while Arad et al showed no effect in females. The number of studies evaluating the effect of HIIT on insulin sensitivity in both genders is low, and further investigations are required.…”

“…Studies have reported that reduced insulin sensitivity in older subjects is due to obesity rather than ageing itself, and visceral fat has been shown to be negatively associated with insulin sensitivity . In the present study, we found reductions in visceral fat and per cent fat which agrees with prior HIIT studies . Visceral fat did correlate negatively with whole‐body insulin sensitivity before and after HIIT, but the changes in these two parameters did not correlate, which implies that they are probably coupled indirectly.…”

“…Robinson et al found an increase in insulin sensitivity in young and older males and females after 12 weeks of HIIT, three times a week, however combined with 45 minutes incline walking twice a week. In young males and females, Richards et al did also report an increase in insulin sensitivity after 6 HIIT sessions, while Arad et al found no change in young overweight and obese women after 14 weeks of HIIT, three times a week. Our finding of improved insulin sensitivity in response to HIIT is supported by most, but not all studies, which have applied surrogate measures of insulin sensitivity using different indexes (HOMA, Cederholm or Matsuda) in young‐ or middle‐aged healthy males and females.…”

“…Exercise has repeatedly been demonstrated to have a positive effect on insulin sensitivity in both young and older subjects . However, to our knowledge whole‐body insulin sensitivity has only been measured once by clamp in older subjects performing HIIT, and in young subjects, only two studies are available at present . Robinson et al found an increase in insulin sensitivity in young and older males and females after 12 weeks of HIIT, three times a week, however combined with 45 minutes incline walking twice a week.…”

“…High‐intensity interval training (HIIT), an alternative to endurance training, is based on low‐volume training at high intensity and is thus more time efficient. The effect of HIIT has been investigated in both young and older subjects in several studies, and overall, HIIT is as effective as moderate‐intensity endurance training to increase maximal oxygen uptake (VO 2 max) and muscle mass and reduce fat mass, including visceral fat . The effect of HIIT on insulin sensitivity has, to our knowledge, only been measured in three studies by the gold standard, the hyperinsulinaemic‐euglycaemic clamp showing no change in young females or an increase in both young and older males and females in whole‐body insulin sensitivity.…”