Thesis (M.A. (Human Movement Science))--North-West University, Potchefstroom Campus, 2009.

Thesis (M.A. (Human Movement Science))--North-West University, Potchefstroom Campus, 2009.

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 4 uppsatser.

Thesis (Ph. D.)--University of Washington, 1997. / Vita. Includes bibliographical references (leaves [78]-85).

Thesis (M.S.)--University of Wisconsin-Madison, 1994. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 31-35).

Thesis (Ph.D.)--University of Alabama at Birmingham, 2010. / Title from PDF title page (viewed on July 7, 2010). Includes bibliographical references.

Fluid intake and regulation are implicated in the control of energy balance and appetite. The studies in this thesis have examined the effects of fluid manipulation on appetite and energy intake. Fifty-eight young, predominantly Caucasian males were recruited to five studies. The age, height and body mass of the subjects were: 24.9 ± 3.8 y, 1.79 ± 0.1 m, 80.1 ± 14.8 kg (mean ± SD) respectively. In Chapter 3, 13 h of hypohydration after exercise in the heat did not influence energy intake at an ad-libitum buffet meal (P=0.436) compared to a euhydrated trial, although greater thirst (P < 0.001) and lower fullness (P < 0.01) was reported in the hypohydration trial. Chapter 4 demonstrated that there was no difference in energy intake or appetite after 24 h of hypohydration either with or without fluid during a semi-solid ad-libitum breakfast. Thirst and fluid intake were greater during the hypohydrated with fluid (HYPO-F; 618 (251) mL) than the euhydrated with fluid (EU-F; 400 (247) mL) trials (P < 0.01). Chapter 5 and 6 showed that a bolus of water (500 mL) immediately before an ad-libitum porridge breakfast reduced energy intake in both healthy and overweight and obese subjects (P < 0.001). The water preload increased fullness and decreased hunger compared to pre-trial in both studies (P < 0.001). In Chapter 7, 75 minutes before an ad-libitum lunch a post-exercise milk (MILK) based drink reduced energy intake (6746 (2035) kJ) compared to an isoenergetic flavoured carbohydrate (CHO) and water based drink (7762 (1921) kJ; 7672 (2005) kJ) (P < 0.05). This thesis has shown that when subjects are hypohydrated, either after exercise or after 24 h of fluid restriction energy intake is not different at an ad-libitum meal. However, there is an increased thirst and subsequent fluid intake before an ad-libitum meal (chapter 3 and 4). This effect was more acutely displayed when a bolus of water was provided immediately before an ad-libitum breakfast meal and subsequently decreased energy intake in both normal and overweight/ obese subjects (chapter 5 and 6). The possible mechanism for this was gastric fill and distension creating satiety before a meal. Chapter 7 has showed that when subjects consume isoenergetic drinks with different energy densities (milk vs CHO and water), before an ad-libitum lunch, energy intake was decreased when milk was consumed. Milk having an increased energy density due to larger protein fractions (casein) may further explain the decrease in energy intake found in chapters 5 and 6 by a similar mechanism. Therefore, gastric fill before a meal decreases ad-libitum energy intake by either the intake of water immediately before a meal or by milk as a more delayed response (75 min). The hydration status however, did not affect energy intake directly in our finding, although it did affect subsequent fluid ingestion, which may have affected findings in chapters 3 and 4.

A number of strategies to lose weight are available. However, a high inter-individual variability is commonly observed in terms of weight loss and its maintenance in individuals enrolled in different interventions. This high variability is mainly explained by individual differences in the activation of compensatory mechanisms triggered by energy deficits. Increases in appetite ratings as well as the rewarding effects of foods are some of the consequences commonly observed from weight loss induced by caloric restriction. On the other side of the energy balance equation, resting energy expenditure (REE) was also found to decrease as consequence of weight loss. Numbers might in fact decrease beyond what could be expected from changes in body weight and composition, highlighting an adaptation in thermogenesis in some individuals. These changes were previously found to be associated with the magnitude of weight loss. However, it is not clear whether different rates of weight loss have a different impact on the compensatory mechanisms described above. Moreover, other questions regarding weight loss maintenance deserve further investigations. For example, the role of exercise, more specifically resistance training (RT), on weight loss maintenance needs additional attention. Accordingly, the present thesis aimed to investigate the effects of caloric restriction on compensatory mechanisms that occur during and after weight loss. We first aimed to determine whether the rate of weight loss differently influence physiological and psychological variables related to energy balance. Secondly, we aimed to elucidate whether early changes in the above mentioned adaptations in energy expenditure (EE) and energy intake (EI) variables predict final outcomes (fat mass - FM and weight loss). Finally, we aimed to determine whether RT promoted greater weight loss maintenance. In Article I and II, we investigated whether different rates of weight loss play a role in EI and EE related-variables. We noted significant increases in fasting appetite measures, as well as increases in satiety measures. REE decreased over time, as did the relative reinforcing value of fruit. No significant group interaction was observed illustrating that different rates of weight loss has no impact on the magnitude of adaptations in EI and EE after weight loss. In article III we demonstrated that early changes in fasting and postprandial appetite measures in response to caloric restriction were associated with greater body weight and FM loss in women. Indeed, greater increases in fasting appetite were associated with greater FM loss, contrary to our hypothesis. However, increases in postprandial appetite were associated with greater FM and body weight loss, independently of changes in eating behaviours. Taken together, articles I and III demonstrated that caloric restriction has a significant impact on increases in appetite and reduction in REE as soon as the in the first week of intervention. Those changes remain significant until the end of the program. In article IV it was shown that 1-year of resistance training (2x/ week) after 6-month of caloric restriction was not sufficient to promote better weight and FM loss in post-menopausal women. Furthermore, the results demonstrated that RT did not improve the differences between measured and predicted measures in REE observed as consequence of weight loss. The picture that emerges is that, increases in appetite and decreases in REE can be observed since the first week of caloric restriction and remain significant until the end of the program, independently of the rate of weight loss. Feeding-related variables such as fasting and postprandial appetite and RRV of a snack food are better predictors of final FM loss, even after adjusting for changes in eating behaviours. In addition, our study demonstrated that different rates of weight loss do not have an independent aspect on either physiological or psychological aspects related to energy balance.

Objectives: This pilot study examined how Methylphenidate (MPH0.5mg/kg) affects appetite sensations, food reinforcement, energy intake (EI), macronutrient consumption, and weight-loss in youth and adults living with obesity, without ADHD. Methods: This study employed a randomized, double-blind, placebo-controlled design. Eleven participants aged 28±6.9 yrs. (4 M, 7 F) were randomized to receive either MPH (n=5) or placebo group (n=6) for 60 days. Participants’ appetite sensations (Visual Analogue Scale), relative-reinforcing value of food (computer task), EI and macronutrient consumption (ad libitum buffet), and anthropometric measurements (DEXA) were measured at baseline and 60 days. Results: Repeated measures ANOVA revealed group x time interactions for appetite sensations [desire to eat (p=0.01), hunger (p=0.002), and prospective food consumption (p=0.006)]; with greater reductions in MPH group compared to placebo. For the sense of fullness, there was an interaction between group and time (p=0.01), with a greater increase for MPH compared to placebo. Body weight significantly decreased in both groups (p=0.01), with a moderate to large effect size favouring the MPH group (-2.66 kg vs. – 1.16 kg, Cohen’s d =0.76). Changes between MPH and placebo did not differ significantly on EI, macronutrient consumption, or food reinforcement. Conclusions: Our data indicate for the first time that MPH suppresses appetite in individuals with obesity resulting in a moderate–sized effect on weight loss in the short-term. These findings warrant a larger trial to more definitively examine the effect that MPH has on weight loss and maintenance of weight loss, thereby evaluating its potential as a novel pharmacological agent in the management of obesity.

Active video games (AVG) have been shown to acutely increase energy expenditure when compared to seated video games; however, the compensatory effects on energy intake and subsequent energy expenditure are largely unknown. The main objective of this thesis was to examine the acute effects of AVG on energy intake and expenditure in male adolescents. Our results suggest that male adolescents compensate for one hour of AVG play by decreasing their physical activity levels for the remainder of the day. There was no compensation in acute energy intake with AVG play. The results from this thesis suggest that the benefits of one hour of Kinect™ AVG play are offset within 24 hours in male adolescents. Therefore, caution must be exercised when prescribing AVG for interventions aimed at preventing/treating childhood obesity.