The Acute Effect of Protein or Carbohydrate Intake on Testosterone Levels and Food Intake in Children and Adolescent Boys

The Acute Effect of Protein or Carbohydrate Intake on Testosterone Levels and Food Intake in Children and Adolescent Boys

The purpose of this study was to determine the effect of acute protein and glucose intake on testosterone levels measured in adolescent boys and determine whether changes in testosterone levels are associated with alterations in short-term food intake. It was hypothesized that 1) ingestion of a protein beverage would result in no change of testosterone levels whereas glucose would result in a significant decrease of testosterone levels 60 minutes after ingestion and 2) decreases of testosterone levels as a result of the glucose preload would predict food intake for boys of similar body size. The first objective was to investigate the effect of an acute protein or glucose drink on testosterone levels and the second objective was to determine whether changes of testosterone levels associate with food intake.

In a randomized, crossover study, sixteen 9-18 y old males were given beverages containing either: 1) whey protein (1g/kg bodyweight), 2) glucose (1g/kg bodyweight) or a calorie-free control (C). Serum testosterone, appetite biomarkers and subjective appetite were measured prior (0) and at 20, 35 and 65 minutes after the consumption of the beverage. Food intake at an ad libitum pizza meal was assessed 20 min later (65-85min).

The experimental beverages contained either 1g of glucose monohydrate (BioShop Canada Inc., Burlington, Ontario, Canada) or 1g of protein (plain whey-protein isolate; BiPro USA., Eden Prairie, Minnesota, U.S.A) per kg of bodyweight. A non-calorie drink was used as control. All beverages were flavoured with 1.5ml of chocolate extract (Vanilla Food Company, Markham, Ontario, Canada) to account for the flavor differences and mixed with 500ml of water. The whey protein and control beverages were sweetened with 0.2g sucralose (Tate & Lyle, Stoney Creek, Ontario, Canada) in order to match sweetness with the glucose beverage.

Participants were given 5 minutes to ingest the non-caloric beverage which contained 1.5ml of chocolate extract (Vanilla Food Company, Markham, Ontario, Canada) to account for the flavor differences and mixed with 500ml of water and sweetened with 0.2g sucralose (Tate & Lyle, Stoney Creek, Ontario, Canada) in order to match sweetness with the glucose beverage.

Participants were given 5 minutes to ingest the beverage which contained either 1g of protein (plain whey-protein isolate; BiPro USA., Eden Prairie, Minnesota, U.S.A) per kg of bodyweight and was flavoured with 1.5ml of chocolate extract (Vanilla Food Company, Markham, Ontario, Canada) to account for the flavor differences and mixed with 500ml of water.

Participants were given 5 minutes to ingest the beverage which contained 1g of glucose monohydrate (BioShop Canada Inc., Burlington, Ontario, Canada) per kg of bodyweight and flavoured with 1.5ml of chocolate extract (Vanilla Food Company, Markham, Ontario, Canada) to account for the flavor differences and mixed with 500ml of water.

The first blood draw was taken prior to ingesting the experimental beverage at baseline (0 minutes). Participants were then given 5 minutes to ingest the beverage, and blood was later obtained 20, 35 and 65 minutes after baseline blood draw. Units were measured in ng/dl.

Visual Analog Scales were employed to assess subjective appetite based on the Determination to Eat. Units were measured in mm (based on a 100mm scale).

Visual Analog Scales were employed to assess subjective appetite based on feelings of Hunger. Units were measured in mm (based on a 100mm scale).

Visual Analog Scales were employed to assess subjective appetite based on feelings of FullnessUnits were measured in mm (based on a 100mm scale).

Visual Analog Scales were employed to assess subjective appetite based on Prospective Food Consumption. Units were measured in mm (based on a 100mm scale).

Participants were provided an ad libitum pizza meal. The participants were instructed to eat during the next 20 min until they were comfortably full. Based on the participant preferences determined during screening, two varieties of Deep 'N Delicious 5-inch-diameter pizza were provided for consumption; pepperoni and three-cheese pizzas (McCain Canada Ltd., Florenceville, Ontario, Canada). Units were measuring in kcal.

Normal weight and overweight/obese adolescent males (n=34) age 9 to 18 were recruited via print advertisement in the local Toronto newspaper. verweight was categorized as in the 85th-95th percentile and obesity in ≥95th percentile.

Inclusion Criteria: 9-18 years, healthy, male. Exclusion Criteria: History of prematurity, chronic illness, were taking any medications known to affect glucose homeostasis, appetite or pubertal development.

Individual participant data will not be made available to other researchers.Participant's identities will be kept confidential. Records will be kept in a locked filing cabinet in the Fitzgerald building at 150 College Street, room 305. Access will be restricted to those directly involved with the project, such as the investigator and the co-investigators. Following recruitment and attainment of informed consent, participants will be given an ID # which will be used on all forms and data analysis. Informed consent forms will be kept in a locked cabinet in a locked office, contain participant names. Research records will be identified by initials, ID number, test and date. Results identified by date and ID number will only be entered on password-protected personal computers kept in locked laboratories or offices at the University of Toronto. Any electronic data will be held on encrypted computers and USB sticks for the same period of time.

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