Effects of nutrient and exercise interactions on the components of energy balance

Podestá Donoso, Israel ORCID: 0000-0002-0301-4913 (2024). Effects of nutrient and exercise interactions on the components of energy balance. University of Birmingham. Ph.D.

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Abstract

Obesity and overweight are rising worldwide. One common strategy to manage body mass is to modify physical activity levels. However, in most cases, the effects of increasing physical activity or exercise are not reflected in body mass changes, possibly due to the trigger of changes in the components of energy balance to counteract the energy deficit. Metabolically, it has been suggested that carbohydrate availability/metabolism (e.g., glucostatic, glycogenostatic or hepatostatic theories) could play a role in modulating the changes in the components of energy balance as a signal of energy availability. The aim of this thesis was to investigate how, from a metabolic perspective, dietary carbohydrates and physical activity/exercise interact in the short term to modulate energy balance components (such as energy expenditure, energy intake, and appetite).

Chapter 3 explored the short-term effects of replacing exercise energy expenditure with a high carbohydrate/low fat (HCLF) or a low carbohydrate/High fat drink (LCHF) on energy balance components. After the exercise energy expenditure was replaced with two different drinks, participants were studied across four days, where appetite, energy intake, activity- and total energy expenditure were evaluated. This chapter showed two novel findings - an increased cumulative activity energy expenditure and a decreased appetite for the HCLF treatment compared with LCHF condition. Therefore, it showed that a nutritionally different energy replacement post-exercise could lead to divergent responses on energy balance and appetite components.

Following these observations, Chapter 4 investigated the effects of a carbohydrate-fed (FEDex) versus an overnight-fasted (FASTex) exercise bout on the components of energy balance (i.e., energy intake, activity and total energy expenditure, appetite) and interstitial glucose metric across four days. Although no significant differences between the two conditions were observed, the study expanded the previously published data time frame, providing a more comprehensive understanding of acute and long-term energy balance studies. The findings suggest that both approaches could be used interchangeably as exercise strategies for body mass management.

Finally, Chapter 5 investigated the relationship between the habitual diet of individuals, considering both nutrients and energy intake, and their physical activity energy expenditure (AEE). The study was conducted using data from the UK Biobank cohort, where a Random intercept model was fitted from 52,643 participants. The study tested the predictability of two models - one including carbohydrate and energy intake, and the other including only carbohydrate intake - on the AEE levels. Although both models predicted around the same percentage of the variance (~2%) for AEE, the model that only included carbohydrates presented a better goodness of fit/complexity ratio according to the Akaike Index Criterion (AIC). These findings showed that habitual carbohydrate intake weakly but significantly predicts AEE levels in the UK Biobank cohort, suggesting that the effects of carbohydrates are not only due to their energy content but also their metabolic effects.
Overall, this thesis has provided new data suggesting that carbohydrate availability/metabolism around exercise/physical activity can affect AEE and appetite differently. These results fit some features of previous theories (e.g., glucostatic, glycogenostatic, and hepatostatic), although the observed responses are weaker than previously thought.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):