Multiple short bouts of exercise over 12-h period reduce glucose excursions more than an energy-matched single bout of exercise

Inverse association between carbohydrate consumption and plasma adropin concentrations in humans

OBJECTIVE

The role of metabolic condition and diet in regulating circulating levels of adropin, a peptide hormone linked to cardiometabolic control, is not well understood. In this study, weight loss and diet effects on plasma adropin concentrations were examined.

METHODS

This report includes data from (1) a weight loss trial, (2) an evaluation of acute exercise effects on mixed-meal (60% kcal from carbohydrates) tolerance test responses, and (3) a meta-analysis to determine normal fasting adropin concentrations.

RESULTS

Distribution of plasma adropin concentrations exhibited positive skew and kurtosis. The effect of weight loss on plasma adropin concentrations was dependent on baseline plasma adropin concentrations, with an inverse association between baseline and a decline in concentrations after weight loss (Spearman's ρ = -0.575; P < 0.001). When ranked by baseline plasma adropin concentrations, only values in the upper quartile declined with weight loss. Plasma adropin concentrations under the main area of the bell curve correlated negatively with habitual carbohydrate intake and plasma lipids. There was a negative correlation between baseline values and a transient decline in plasma adropin during the mixed-meal tolerance test.

CONCLUSIONS

Plasma adropin concentrations in humans are sensitive to dietary macronutrients, perhaps due to habitual consumption of carbohydrate-rich diets suppressing circulating levels. Very high adropin levels may indicate cardiometabolic conditions sensitive to weight loss.

Benefits for Type 2 Diabetes of Interrupting Prolonged Sitting With Brief Bouts of Light Walking or Simple Resistance Activities

OBJECTIVE

To determine whether interrupting prolonged sitting with brief bouts of light-intensity walking (LW) or simple resistance activities (SRA) improves postprandial cardiometabolic risk markers in adults with type 2 diabetes (T2D).

RESEARCH DESIGN AND METHODS

In a randomized crossover trial, 24 inactive overweight/obese adults with T2D (14 men 62 ± 6 years old) underwent the following 8-h conditions on three separate days (with 6-14 days washout): uninterrupted sitting (control) (SIT), sitting plus 3-min bouts of LW (3.2 km · h(-1)) every 30 min, and sitting plus 3-min bouts of SRA (half-squats, calf raises, gluteal contractions, and knee raises) every 30 min. Standardized meals were consumed during each condition. Incremental areas under the curve (iAUCs) for glucose, insulin, C-peptide, and triglycerides were compared between conditions.

RESULTS

Compared with SIT, both activity-break conditions significantly attenuated iAUCs for glucose (SIT mean 24.2 mmol · h · L(-1) [95% CI 20.4-28.0] vs. LW 14.8 [11.0-18.6] and SRA 14.7 [10.9-18.5]), insulin (SIT 3,293 pmol · h · L(-1) [2,887-3,700] vs. LW 2,104 [1,696-2,511] and SRA 2,066 [1,660-2,473]), and C-peptide (SIT 15,641 pmol · h · L(-1) [14,353-16,929] vs. LW 11,504 [10,209-12,799] and SRA 11,012 [9,723-12,301]) (all P < 0.001). The iAUC for triglycerides was significantly attenuated for SRA (P < 0.001) but not for LW (SIT 4.8 mmol · h · L(-1) [3.6-6.0] vs. LW 4.0 [2.8-5.1] and SRA 2.9 [1.7-4.1]).

CONCLUSIONS

Interrupting prolonged sitting with brief bouts of LW or SRA attenuates acute postprandial glucose, insulin, C-peptide, and triglyceride responses in adults with T2D. With poor adherence to structured exercise, this approach is potentially beneficial and practical.

Dose-response association of physical activity with HbA1c: Intensity and bout length

OBJECTIVE

The aims of this study were to characterize the dose-response relationship between moderate-to-vigorous intensity physical activity (MVPA), and light-intensity activity with HbA1c in adults at low, moderate, and high risks of type 2 diabetes, and to compare the relationship of short (1 to 9min) versus long (10+min) bouts of MVPA with HbA1c.

METHODS

Data from 2707 participants from the 2003-2006 National Health And Nutrition Examination Survey were analyzed in 2014-2015. Type 2 diabetes risk was classified into three groups based upon age (<40years; ≥40years) and BMI (<30; ≥30). The relationship between HbA1c and accelerometer-based physical activity variables was assessed using multiple regression models.

RESULTS

There was a curvilinear dose-response relationship between HbA1c with total activity and MVPA in adults at moderate or high risk for type 2 diabetes: higher amounts of physical activity were associated with lower HbA1c. The association of physical activity on HbA1c was stronger at lower levels of physical activity. There was no dose-response relationship in adults at low risk for type 2 diabetes. The relationship between short bouts with HbA1c was stronger than for bouts≥10min.

CONCLUSIONS

In adults at risk for type 2 diabetes, there is a dose-response relationship between physical activity and HbA1c levels such that the relationship: (1) is curvilinear; (2) is stronger when a higher percent of total activity comes from MVPA; and (3) is more potent with short bouts of MVPA. Fractionalized physical activity of at least moderate-intensity may contribute to long-term glucose control.

Meta-analysis of the relationship between breaks in sedentary behavior and cardiometabolic health

OBJECTIVE

The concept of "breaks" in sedentary behavior has emerged as a potential modifier of detrimental effects on adiposity caused by sedentary behavior. The existing research investigating the relationship between breaks in sedentary behavior with adiposity and cardiometabolic health in adults was systematically reviewed and quantitatively synthesized by this study.

METHODS

Observational and experimental studies that examined the relationships between the frequency of interruptions of sedentary behavior and markers of adiposity and cardiometabolic health in adults were identified by a systematic search of the literature. A meta-analysis was conducted by using the inverse variance method for experimental trials and a Bayesian posterior probability of existence of an association between breaks with adiposity and cardiometabolic markers for observational studies.

RESULTS

It was revealed by the pooled results from nine experimental studies that breaks in sedentary periods of at least light intensity may have a positive effect on glycemia but not on lipidemia for adults. It is unclear whether this effect is independent of total sitting time. However, the 10 identified observational studies showed an association with breaks, which was independent of total sedentary time, but only for obesity metrics.

CONCLUSIONS

The theory that interrupting bouts of sedentary behavior with light-intensity activity might help control adiposity and postprandial glycemia was supported by the evidence. Further investigations with better methods of measuring sedentary behavior patterns and improved study designs are necessary to confirm this preliminary evidence.

Effects of prior exercise on glycemic responses following carbohydrate inges on in individuals with type 2 diabetes

BACKGROUND

Exercise is effective in reducing glycemia, especially when it is performed in the postprandial period. However, no consensus exists in the literature about the effect of exercise on postprandial glucose control when it is performed before carbohydrate consumption.

AIMS

The main aim was to determine whether 20 min of exercise performed prior to carbohydrate consumption reduces postprandial glycemic and insulinemic responses. A secondary aim was to analyze the effectiveness of short-term (10 min) exercise bout with respect to postprandial glycemia reduction.

METHODS

Nine individuals with type 2 diabetes (54.9 ± 1.7 years; 30.7 ± 1.8 kg/m²; glycemia level of 167.0 ±10.6 mg/dL) participated in the study and underwent the following procedures: (a) an incremental test to determine the lactate threshold; (b) an exercise session for 20 minutes at moderate intensity (90% of the lactate threshold); and c) a control session. The last two sessions were randomized, and the participants were monitored during 135 minutes of post-exercise recovery. A standard meal was consumed two hours before the experimental procedures started. A dextrose solution was administered at 45 minutes of post-exercise recovery while monitoring glucose and insulin concentrations. At 135 min of post-exercise recovery, eight of the participants performed an additional 10-min exercise bout following induced hyperglycemia.

RESULTS

Exercise reduced glycemia (-46.6 ± 7.9 mg/dL) and the insulin/glucose ratio (from 1.73 ± 0.59 to 0.93 ± 0.22 µU/mL/mmol/L) during the first 45 minutes of post-exercise recovery. Glycemia was significantly increased after carbohydrate consumption, reaching its peak value at 105 minutes of post-exercise recovery (261.8 ± 15.8 mg/dL) or control (281.3 ± 13.4 mg/dL). There was no effect of the previous exercise in attenuating glycemia or reducing the area under the curve for glucose and insulin after carbohydrate consumption. However, the effectiveness of exercise in reducing glycemia was shown again when it was performed at the end of the experimental session, even in case of only a 10-min exercise (reduction of -44.5 ± 4.9 mg/dL).

CONCLUSIONS

Twenty minutes of moderate exercise does not alter the kinetics or the area under the curve in terms of glycemia and insulinemia after subsequent carbohydrate consumption. However, moderate exercise, even if performed for only 10-20 minutes, is effective in reducing postprandial glycemia in individuals with type 2 diabetes.

RELEVANCE FOR PATIENTS

Moderate-intensity exercise, even of short duration, may benefit individuals with type 2 diabetes on blood glucose control. A fast reduction in postprandial glycemia can be obtained with only ten minutes of exercise that, in turn, may ameliorate some of complications associated with the disease.

Managing sedentary behavior to reduce the risk of diabetes and cardiovascular disease

Modern human environments are vastly different from those of our forebears. Rapidly advancing technology in transportation, communications, workplaces, and home entertainment confer a wealth of benefits, but increasingly come with costs to human health. Sedentary behavior-too much sitting as distinct from too little physical activity-contributes adversely to cardiometabolic health outcomes and premature mortality. Findings from observational epidemiology have been synthesized in meta-analyses, and evidence is now shifting into the realm of experimental trials with the aim of identifying novel mechanisms and potential causal relationships. We discuss recent observational and experimental evidence that makes a compelling case for reducing and breaking up prolonged sitting time in both the primary prevention and disease management contexts. We also highlight future research needs, the opportunities for developing targeted interventions, and the potential of population-wide initiatives designed to address too much sitting as a health risk.