8:00 am - 9:00 am
A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES PhD Final Exam Seminar by Camila Lemos Pinto Oliveira. This seminar is open to the general public to attend.
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Meeting ID: 923 2053 3150
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Meeting ID: 923 2053 3150
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Thesis Topic: Effects of a High-Protein Diet Replacement on Energy Homeostasis in Healthy Adults
PhD with Dr. Carla Prado.
Seminar Abstract: Lifestyle modifications that induce energy deficit, such as diet and physical activity, are
considered the cornerstone of weight management. The overall purpose of this research was to
compare the effects of an acute nutritional intervention comprised of a high-protein (HP) diet
replacement versus a standard North American dietary pattern on selected components of energy
metabolism, metabolic blood markers, appetite sensations, and appetite-related hormones in
healthy, normal-weight adults of both sexes.
Three studies are presented as part of two complementary randomized, controlled, crossover
clinical trials conducted separately in men and women. Two studies explored the impact of
two isocaloric nutrition interventions in healthy, normal-weight adults: a) high-protein total diet
replacement (HP-TDR): 35% carbohydrate, 40% protein, and 25% fat achieved through a
nutritional supplement; b) control (CON): 55% carbohydrate, 15% protein, and 30% fat.
Participants received the prescribed diets for 32 hours while inside a whole-body calorimetry unit
(WBCU). The first dietary intervention randomly offered in the WBCU was designed to maintain
energy balance and the second matched what was offered during the first stay.
The last study was a sub-analysis involving the isocaloric breakfasts during the WBCU
stay: a) high-protein meal replacement (HP-MR): 30% carbohydrate, 43% protein, and 27% fat
achieved through a nutritional supplement; b) CON: 55% carbohydrate, 15% protein, and 30% fat.
Following breakfast, participants performed a moderate-intensity aerobic exercise session. The
following physiological changes were compared between groups: energy expenditure, energy
balance, macronutrient oxidation rates and balances, metabolic blood markers, appetite sensations,
and appetite-related hormones. Body composition was assessed at baseline using dual-energy Xray
absorptiometry.
In total, forty-three healthy, normal-weight adults (56% males) were included. Compared
to the CON diet, the HP-TDR produced higher total energy expenditure (HP-TDR: 2143 ± 268
kcal/day; CON: 2061 ± 243 kcal/day; p<0.001), protein (HP-TDR: 91 ± 40 g/day; CON: 53 ± 20
g/day; p<0.001) and fat oxidation rates (HP-TDR: 79 ± 17 g/day; CON: 71 ± 16; p=0.013), and
lower carbohydrate oxidation rate (HP-TDR: -48 ± 33 g/day; CON: 22 ± 26 g/day; p<0.001).
Moreover, a HP-TDR led to decreased energy (-112 ± 85 kcal/day; p<0.001), fat (-22 ± 20 g/day;
p<0.001), and carbohydrate balances (-69 ± 44 g/day; p<0.001), and increased protein balance (90
± 32 g/day; p<0.001).
In the HP-TDR, only females experienced lower 24-h area under the curve for prospective
food consumption, and higher composite satiety score after breakfast day 1, before lunch, and
before dinner. Compared to the CON diet, change in appetite-related hormones from fasting day
1 to fasting day 2 during the HP-TDR intervention was smaller for peptide tyrosine-tyrosine (PYY)
and greater for leptin. Moreover, postprandial levels of glucagon-like peptide 1 (GLP-1) and PYY
were higher in the HP-TDR.
In the last study, compared to the CON breakfast, the HP-MR produced higher fat oxidation
(1.07 ± 0.33 g/session; p=0.003) and lower carbohydrate oxidation (-2.32 ± 0.98 g/session;
2
p=0.023) and respiratory exchange ratio (-0.01 ± 0.00; p=0.003) during the exercise. After the
exercise, increases in hunger were lower during the HP-MR condition. Changes in blood markers
from the fasting state to post-exercise during the HP-MR condition were greater for insulin, PYY,
and GLP-1, and lower for low-density lipoprotein cholesterol, triglyceride, and glycerol.
The major findings of this thesis were that, compared to a North American dietary pattern,
a HP diet replacement improved selected components of energy metabolism favoring body weight
and fat losses at rest and during exercise, partly improving individual’s metabolic profile, and
eliciting changes in appetite sensations and appetite-related hormones that reflect decreased hunger
and increased satiety. Additionally, females and males responded differently to the dietary
interventions with respect to appetite sensations and appetite-related hormones. Overall, females’
response to the HP diet replacement was more pronounced in terms of appetite sensations, while
in males this response was mostly related to appetite-related hormones. Findings from this research
contribute to the body of literature pertaining to the effects of a HP diet replacement and physical
activity. Collectively, they provide further insight into the potential role of these strategies for
weight maintenance and prevention of obesity.
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