Bariatric Times

AUG 2017

A peer-reviewed, evidence-based journal that promotes clinical development and metabolic insights in total bariatric patient care for the healthcare professional

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14 Medical Methods in Obesity Treatment Bariatric Times • August 2017 CURRENT EVIDENCE ON HIIT IN INDIVIDUALS WITH OVERWEIGHT AND OBESITY Though not included in the existing physical activity guidelines, HIIT is increasingly being studied, and researchers are arriving at v arying conclusions. Some research has proven the effectiveness of HIIT in individuals with overweight and obesity, pointing to improvements in cardiovascular and metabolic risk f actors. 6 ,7 One argument for the employment of HIIT is time effectiveness. Growing evidence also shows that through HIIT, individuals might achieve the benefits of traditional continuous exercise training (e.g., increased cardiorespiratory fitness and insulin sensitivity) in 50 to 60 percent of the training time. 1,7,8 However, some researchers, some in the same groups that confirmed the time- efectiveness of HIIT, found that HIIT is lacking in key physiologic effects of exercise, such as the thermogenic response to β- adrenergic stimulation, maximal cardiac output, and fat distribution, a conclusion that tests the time- saving attractiveness of this alternate exercise form. 9 In a recent study by Keating et al, 1 researchers compared low- intensity continuous exercise to HIIT training. Thirty-eight adults who were determined to be inactive (exercising <3 days/week) and have overweight (BMI 25kg/m 2 to 29.9kg/m 2 ) were randomized to one of three groups: HIIT, continuous exercise training (CONT), or placebo group (PLA), for 12 weeks. The HIIT program comprised three sessions per week of high-intensity bursts (i.e., 120 percent peak rate of oxygen consumption [VO 2 peak]), of exercise interspersed with low- intensity exercise for a total of 20 to 24 minutes per session. The CONT group performed continuous exercise at 50 to 65 percent VO 2 peak for a total time of 36 to 48 minutes per session. The protocol was designed such that both exercise groups would generate an isocaloric energy expenditure. The PLA group performed a sham exercise program of stretching, self- massage, and fitball designed not to elicit any cardiometabolic improvements. After 12 weeks of exercise, improvement in fitness measure by W peak was similar in the HIIT and CONT group and significantly better than the PLA group. These results demonstrated the benefit of HIIT being able to produce improvement i n fitness level with only 50 to 60 percent of the time commitment compared with CONT. However, the CONT group showed a reduction in total body fat, whereas the HIIT g roup did not. The authors found that while HIIT is a time-effective means of achieving improved fitness, it did not reduce total body fat and android fat in previously inactive, overweight adults when compared to continuous aerobic exercise. They concluded HIIT should not be promoted as a time- effective means of increasing fat loss and improving fat distribution for the patient population with overweight. Similarly, Kemmler et al 1 0 found that HIIT provided more weight loss than moderate intensity continuous exercise (MICE) but resulted in no difference in body fat mass. In this study, 81 participants were randomized to a HIIT group, MICE group, or control group for 16 weeks. The HIIT group ran for a total of 25 to 45 minutes per session. During the high-intensity phase, participants ran at 85 to 97.5 percent of their maximum heart rate followed by low-intensity jogging or fast walking at 65 to 70 percent of their maximum heart rate. The MICE group ran from 35 to 90 min per session to maintain at a constant pace to maintain 70 to 82.5 percent of their maximum heart rate. The protocols were designed to generate isocaloric conditions and comparable workload in both exercise groups. Exercise sessions increased from two sessions per week at baseline to 3 to 4 sessions per week after Week 8. At 16 weeks, both groups showed significant but comparable reductions in metabolic risk factors compared to the control group. The MICE participants saw a greater reduction in weight compared to the HIIT participants. However, body composition analysis found that the reduction in body fat was similar for both exercise groups and the greater reduction in body weight loss for MICE was due to a decrease in lean body mass. Conversely, a study by Martins et al 11 did not elicit any significant d ifference between HIIT, short- duration HIIT (1/2HIIT), and moderate-intensity continuous training (MICT) on body composition or cardiovascular f itness. In this study, 46 sedentary individuals with obesity were randomly assigned to one of three groups: HIIT, 1/2HITT, or MICT for 12 weeks. Each group participated i n stationary bicycling three days per week. The HIIT protocol comprised eight seconds of sprinting followed by 12 seconds of recovery to induce an energy expenditure of 250 kcal. The 1/2HIIT protocol was identical to the HIIT protocol except it was limited to induce only 125 kcal expenditure. The MICT group participated in continuous cycling at 70 percent of maximum heart rate for a 250 kcal expenditure. Each of the groups experienced improvements in body composition (loss of fat and increase in fat free mass) and cardiovascular fitness, though no form proved significant in these areas. DISCUSSION Professional guidelines and the available literature highlight that the benefits of exercise for treatment of overweight and obesity should not be measured by counting caloric expenditure alone. While the law of thermodynamics does apply, the complexities of human physiology determine changes in body composition in response to exercise. Also, it is well known that there is large variability in individual response to exercise. 12 Though most recommendations for treatment of overweight and obesity include exercise, meta- analyses have demonstrated that the addition of exercise to a diet program provides only nominal improvements in weight loss. 13 However, we do know that improvements in T2DM and reduction in abdominal fat can be obtained even when exercise produces no weight loss benefit. 14,15 Given that lack of time is the number one reported barrier to an individual's participation in regular physical activity, 16 HIIT might be advantageous in acquiring similar cardiovascular fitness compared to e xercise of a longer duration. HIIT also appears to be better at maintaining muscle mass than traditional continuous exercise; however, these studies demonstrate t hat continuous exercise appears to be more effective for weight loss and specifically for causing loss of fat mass. Research provides some insight i nto HIIT and its effect on obesity, though it is important to note that there is wide variability in HIIT across studies regarding length of exercise, type of exercise, and m easurement of "high-intensity;" therefore, these results might not be generalized to all types or durations of HIIT. CONCLUSION Studies available on HIIT in the patient population with overweight and obesity remain limited by their short duration, small number of p articipants, and variation in intensity and duration of "on" intervals; therefore, further research is needed. As with many other medical regimens, exercise can be a joint decision that includes input from the patient. When prescribing exercise regimens to patients, clinicians might aim to learn what type of exercise the individual enjoys and can perform regularly. This approach supports the old adage that the best exercise we can prescribe for our patients is the one they are willing to do. If a patient expresses interest in HIIT, encourage him or her to evaluate the available evidence while considering the safety of the exercise according to their current physical state, which can be assessed by an appropriate pre- exercise screening test. REFERENCES 1. Keating SE, Machan EA, O'Connor HT, et al. Continuous exercise but not high intensity interval training improves fat distribution in overweight adults. J Obes. 2014;2014:834865. 2. U.S. Department of Health and Human Services. 2008 Physical Activity Guidelines for Americans. Washington, DC: U.S. Department of Health and Human Services, 2008. 3. Wing R, Phelan S. Long-term weight loss maintenance. Am J Clin Nutr. 2005 Jul;82(1 Suppl):222S–225S. 4. Jensen, MD, Ryan DH, Apovian CM, et al. 2014. 2013 AHA/ACC/TOS Guideline for the Management of Overweight and Obesity in Adults. Circulation. 2014;129(25 Suppl 2):S102–138. 5. Garvey WT, Mechanick JI, Brett EM, et al. American Association of Clinical Endocrinologists and American College of Given that lack of time is the number one reported barrier to an individual's p articipation in regular physical activity, 1 6 H IIT might be advantageous in acquiring s imilar cardiovascular fitness compared to exercise of a longer duration. HIIT also a ppears to be better at maintaining muscle mass than traditional continuous exercise; however, these studies demonstrate that continuous exercise appears to be more effective for weight loss and specifically for causing loss of fat mass.

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