<p>Obesity has ascended to become the
primary modifiable cause of death in the United States. New evidence has called
into question the utility of BMI – the typical index of obesity – in predicting
cardiometabolic disturbances. The distribution of body fatness may be just as
important as the total quantity. Intermuscular adipose tissue (IMAT) has
emerged as a distinct subset of adipose in skeletal muscle that may be
particularly metabolically deleterious. Typically,
sections of either the calf or thigh are used as proxy measurements for
whole-body IMAT in investigations. However, IMAT dispersion may not be
consistent across tissues, instead infiltrating specific muscle or muscle
compartments, and these have may have different metabolic consequences. The study
described in Chapter 2 was designed to address this possibility and investigate
and compare associations among thigh and calf IMAT stores with indices of
cardiometabolic health. The strength of the relationship between IMAT and
glucose control-related indices of cardiometabolic health was dependent upon anatomic
location. Specifically, thigh IMAT is a better predictor of cardiometabolic
risk that calf IMAT. </p>
<p>Skeletal muscle has gained
increased recognition in recent years for its importance in promotion of health
and wellness throughout the life course. While treatment models addressing issues
of declining muscle mass and strength with age previously focused on older
adults, the importance of utilizing a life course model to promote skeletal muscle
health at all ages was more recently recognized. There is consistent evidence
that higher-protein diets modestly improve body composition. However, women are
at greater risk for not meeting protein requirements and seem to be less
willing to adopt strategies to achieve greater protein intake, such as protein
supplementation, for fear that it may cause ‘bulkiness’. Therefore, the study described
in Chapter 3 was designed to critically evaluate the effect of whey protein
supplementation on body composition changes in women via a systematic review
& meta-analysis of published randomized controlled trials. It was
hypothesized that whey protein supplementation would moderately improve body composition
but would not cause excessive muscle hypertrophy. Consistent with our
hypothesis, whey protein supplementation improved body composition by modestly
(<1%) increasing lean mass, without influencing fat mass.</p>
<p>Dietary protein and skeletal muscle
are conceptually inseparable; protein is often only considered in terms of how
it impacts skeletal muscle-related outcomes. However, it is of interest to
determine if the proposed beneficial effects of increased dietary protein
consumption extend beyond skeletal muscle. Consumption of higher protein diets
result in lower resting blood pressure, but the potential for protein to
attenuate acute exercise blood pressure responses is unclear. The study described
in Chapter 4 was designed to investigate the effects of meals with different
amounts of protein on blood pressure responses to exercise in a randomized,
cross-over trial. We hypothesized that consuming the higher-protein meal would
attenuate the blood pressure responses to exercise and result in a more robust
post-exercise hypotensive response. Contrary to our hypothesis, a higher-protein
meal does not attenuate exercise-induced blood pressure responses compared to a
lower-protein meal. These findings build upon previous research suggesting that
the beneficial effect of chronically elevated protein intake on blood pressure
is typically not observed in an acute setting by extending these findings to
encompass blood pressure responses to acute responses to exercise.</p>
<p>The three studies packaged herein
utilize different techniques and report on different outcomes, but conceptual
threads unite these works which augment the collective findings. Future
researchers investigating the effects of protein on skeletal muscle anabolism
can: 1) learn of the importance of proper reflection on surrogate measures and
potential for anatomic-specific effects from the IMAT findings (Chapter 2), 2)
appreciate the relevance of energy and training states in modulating responses
from the WP meta-analysis (Chapter 3), and 3) recognize the importance of
holistic approaches and employing challenges to reveal heterogeneity from the
protein and BP trial (Chapter 4). Taken together, the research presented
in this dissertation forwards our understanding of the relations and effects of
dietary protein with different components of body composition on
cardiometabolic health. </p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/12250052 |
| Date | 06 May 2020 |
| Creators | Robert E Bergia (8801123) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/Relations_and_effects_of_dietary_protein_and_body_composition_on_cardiometabolic_health/12250052 |
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