Canadian Science Publishing sponsors the Applied Physiology, Nutrition, and Metabolism Undergraduate Research Excellence Awards, which are awarded by Canadian Science Publishing in partnership with the Canadian Society for Exercise Physiology and the Canadian Nutrition Society. In 2015, Kerry Miller won the award for her research, “Role of sugar-sweetened beverages and short-duration exercise on subjective appetite and glycemic response in 9-14 year old boys.” In this post, Kerry talks about her work and experience working in the lab at the School of Nutrition, Ryerson University.
For the past three years, I have had the pleasure of working for my supervisor, Dr. Nick Bellissimo, Associate Professor at Ryerson University, running clinical research trials and managing his Nutrition Discovery Labs. Together, the laboratories (FIRST – Food Intake & Satiety Testing; NExT – Nutrition & Exercise Testing; BAD – Biomarker Analysis & Discovery) focus on exploring the relationships among nutrient composition, exercise, hormonal and environmental factors that lead to obesity in children.
Dr. Bellissimo’s research program is unique in that his undergraduate students primarily run the lab operations, offering invaluable experiential learning opportunities to this group. Through FIRST and NExT, I have gained hands-on experiences that cannot compare to what is taught in a classroom setting. Most of what I have learned in applying nutrition-related laboratory techniques, management principles, scientific writing and knowledge translation occurred while leading my research project, “Role of Sugar-Sweetened Beverages and Short-Duration Exercise on Subjective Appetite and Glycemic Response in 9-14 Year Old Boys”, for which I was awarded the APNM Undergraduate Research Excellence Award. I am extremely passionate about this area of research and value the opportunity to be able to share the results of my project with a larger academic audience.
The Big Picture – Why Was the Research Conducted?
It is already well established that obesity is a risk factor for type 2 diabetes (T2D); a condition where the body’s cells don’t function properly removing glucose (sugar) from the bloodstream. Although this relationship is commonly identified in adults, concurrent with the existing childhood obesity epidemic, there has been a dramatic increase in the incidence of T2D within the pediatric population. In Canada, approximately 95% of children with T2D are obese at diagnosis and 8% are younger than 10 years of age.
Caloric beverages comprise approximately 20% of daily energy intake in children and adolescents. As a result, sugar-sweetened beverages, including flavoured milk, have been hypothesized as major contributors to obesity. We previously reported, however, that pre-meal consumption of 350 ml of 1% chocolate milk decreases food intake at an ad-libitum test meal 60 minutes later in young girls. Milk consumption is also associated with improved diet quality and in meeting recommendations for several shortfall nutrients. The mechanism of the milk’s suppressant effect and its possible impact on glycemic response is unknown, but further investigations are merited as this is a popular dairy beverage, among children in particular.
Exercise is promoted as a means to improve glycemic control and healthy body weights. Specifically, short, repeated bouts of activity are being encouraged as a way for both children and adults to meet recommended physical activity guidelines. However, research evaluating the impact of short-duration (10-15 minutes) exercise on acute glycemic control is limited and moderate intensity exercise of this duration has been shown to increase motivation-to-eat in some children.
The aim of our study was to understand the role of common snack beverages, with and without exercise, on glycemic regulation and subjective appetite in children. More specifically, we wanted to investigate the effects of chocolate milk compared to a commercial fruit drink, consumed as a mid-morning snack prior to short-duration exercise (as might be combined during a typical school day, i.e. at recess).
How Was the Research Conducted?
The pilot study was structured as a 2×2, within subject repeated measures design, and eight boys ages 9 to 14 participated. At an initial screening session, subjects had anthropometric measures taken and performed a physical fitness test to determine their ventilation threshold (VeT), which is a moderate exertion level estimated to be within 45-65% of a person’s VO2max or maximal aerobic capacity.
For the following four test day sessions, set one week apart, the boys consumed a standardized breakfast two hours prior to their scheduled start time. After arriving at the lab, subjects had baseline measures collected and then were randomly assigned to drink 1% chocolate milk or a fruit drink within five minutes. Both beverages were 250 ml in volume and equally matched for available carbohydrates. Upon completion of the beverage, children either participated in sedentary activities or walked on a treadmill for 15 minutes at their previously determined VeT.
Subject’s motivation-to-eat and physical comfort were periodically measured throughout the test session using visual analogue scales. Blood glucose levels were measured via finger prick following beverage consumption (0 minutes) and exercise or sitting (15 minutes), and at 65 minutes.
What Were the Key Findings?
Moderate intensity, short-duration exercise attenuated glycemic response following the consumption of both sugar-sweetened beverages; and, while both beverages matched for available carbohydrates, chocolate milk and chocolate milk combined with exercise resulted in the lowest blood glucose response over 60 minutes compared with the fruit drink conditions. In addition, exercise was found to have a significant, independent effect increasing the boys` motivation-to-eat.
What Can We Interpret From These Results?
Determining the effect of sugar-sweetened beverages on health outcomes should be a high priority for research because a causal relationship between these drinks and childhood obesity is being speculated despite the lack of literature to support such claims. For example, sugar-sweetened beverages, including flavoured milk, have already been banned for sale in some schools. Results from this pilot study support our previous work that demonstrated chocolate milk’s appetite suppressant effect, when compared to other sugar-sweetened beverages. The dairy beverage was also found to improve glycemic control. So should we treat all sugar-sweetened beverages the same? Considering children are not meeting recommended dairy intakes, and chocolate milk is a source of calcium for growing youth, its exclusion may lead to unintended negative consequences much more impactful on diet quality than the added sugars it contains.
We also wanted to explore the interaction of exercise. On average, exercise bouts led to an energy expenditure of 64 kcals, which when integrated as short, repeated bouts throughout a school day could contribute to weight maintenance. However, exercise also increased the subject’s motivation-to-eat. Further studies measuring food intake, not just subjective appetite, need to be conducted in order to determine which exercise doses indeed promote appetites and food intake. In addition, more research measuring additional markers of glycemic control are required to better understand the physiological relationship between activity, sugar-sweetened beverage consumption and acute energy balance in children.