Body Composition and Lipid Metabolism at Rest and During Exercise: A Cross-Sectional Analysis.
- Conditions
- Lipid MetabolismSubstrate MetabolismExercise
- Interventions
- Behavioral: Study Protocol
- Registration Number
- NCT03029364
- Lead Sponsor
- University of Bath
- Brief Summary
The ability to upregulate fat oxidation at appropriate times such as during fasting, low to moderate intensity exercise and after a high fat meal, is popularly advocated. This is presumably due to the perception that a high capacity to utilise fat may improve (ultra) endurance performance and help in the regulation of body fat and metabolic diseases. In accordance, impaired fat use at rest has been associated with obesity and insulin resistance (Kelley et al., 1999). However, there is inconclusive and / or a lack of systematic evidence, especially in a large diverse range of adults, exploring:
1) Whether whole body fat use during exercise is altered in individuals with overweight or obesity compared to lean individuals
3) The intra-individual variability in whole-body fat use at rest and during exercise
4) Physiological, metabolic, lifestyle and genetic characteristics that are associated with whole-body fat use at rest and during exercise
Therefore, the objectives of this study are three-fold:
1. To explore whether whole body fat use is associated with body composition
2. To explore associations between whole-body fat use and physiological, metabolic, lifestyle and genetic variables
3. To assess the intra-individual variability of whole-body fat use.
This study is an observational, exploratory cross-sectional study. A wide range of 'healthy' and 'at-risk of metabolic disease' adults will be recruited.
Participants will be asked to visit a laboratory at the University of Bath four times. Visit 1 is a screening and study familiarisation visit. Visits 2 and 3 are to be completed within 7-14 days and involve lifestyle monitoring (dietary and physical activity), a one-off urine and blood sample, assessment of fuel use at rest and during exercise (the latter through an incremental graded cycling exercise test to exhaustion). Visit 4 is to assess body composition via a dual-energy x-ray absorptiometry (DEXA) scan in addition to an optional skeletal muscle and / or fat tissue biopsy.
- Detailed Description
Metabolic flexibility broadly refers to the ability to utilize the right fuel source for energy (primarily either carbohydrate or fat) at the right time (Kelley and Mandarino, 2000). This was first conceptualised at the level of skeletal muscle (Kelley and Mandarino, 1990; Andres et al., 1956). A main tenant originally captured by 'metabolic flexibility' is the predominant utilization of fat as an energy source under rested post-absorptive conditions in 'healthy' individuals (Kelley et al., 1999; Kelley and Mandarino, 1990). Recently, there has been a call to extend the concept of 'metabolic flexibility' to exercising conditions (Goodpaster and Sparks, 2017; Rynders et al., 2017). Similarly to at rest, fat provides an important source of energy during low-to-moderate intensity exercise (van Loon et al., 2001; Romijn et al., 1993). Thus, in healthy individuals at the whole-body and skeletal muscle level, it is robustly characterised and accepted that fat is an important and predominant fuel source for energy under such conditions.
However, it is commonly proposed that a lower reliance upon fat as a fuel source is present in individuals with obesity and type 2 diabetes and consequently, has been implicated in the pathogenesis of such conditions (Rynders et al., 2017; Kelley and Mandarino, 2000). Alternatively, a high capacity to utilize fat under the aforementioned two situations is advocated to be a desirable trait for both athletes and non-athletes, presumably due to the perception that high rates of fat utilization may improve endurance performance and/or assist with the regulation of body fat and metabolic health. As such, much interest has been generated into upregulating fat utilization at appropriate times e.g. during fasting and low-to-moderate intensity exercise.
Correspondingly, lower resting and exercising fat use has been reported in individuals with obesity vs lean (e.g. Lanzi et al., 2014; Perez-Martin et al., 2001; Kelley et al., 1999). Furthermore, greater fat use at rest has been associated with lower future body weight and fat gain / regain (e.g. Shook et al., 2016; Seidell et al., 1992), and during exercise with reduced short term post-exercise energy intake / balance (e.g. Hopkins et al., 2012), exercise-induced fat loss (Barwell et al., 2008) and weight loss / maintenance (Dandadell et al., 2017). Importantly, however, this relationship is not always apparent with similar (e.g. Blaize et a., 2014; Croci et al., 2014) or higher (e.g. Ara et al., 2011; Goodpaster et al., 2002; Horowtiz et al., 2000) rates of fat use at rest and during exercise reported in individuals with obesity compared to lean counterparts. Furthermore, cross-sectional and prospective associations do not always exist between lower fat use and greater body weight / fat mass gain or regain (e.g. Dandanell et al., 2017; Ellis et al., 2010). Thus, despite being popularly advocated, it is currently unclear whether lower fat use at rest or during exercise predisposes or is a characteristic of excess adiposity (i.e. obesity).
The inconsistent findings could partly be due to numerous methodological discrepancies between studies such as participant characteristics, matching of comparative groups, the exercise protocol utilised and / or the assessment of body composition, lipid oxidation and cardio-respiratory fitness levels.
Therefore, through the use of well-established and respected techniques, we aim to comprehensively and systematically explore whether whole-body fat use at rest and during exercise is:
1. Altered in individuals with overweight or obesity compared to lean individuals
2. Further determinants / factors that may influence fat use
3. The intra-individual variation in fat use which will help to more confidently determine the above objectives.
Recruitment & Eligibility
- Status
- COMPLETED
- Sex
- All
- Target Recruitment
- 114
- be between 18 - 65 years of age
- male or female
- body mass index between 18.9 - 35 kg/m2
- be able and willing to give informed oral and written consent
- complete and meet the defined criteria of pre-study questionnaires and screens
- Currently have or have a previous history of metabolic, cardio-pulmonary or musculoskeletal disease
- BMI below 18.9 or above 35 kg/m2
- Have plans to change lifestyle (diet and/or physical activity) during the study period ( 7 - 21 days)
- Unwillingness or unable to sufficiently meet study demands
Study & Design
- Study Type
- OBSERVATIONAL
- Study Design
- Not specified
- Arm && Interventions
Group Intervention Description Male and Female Adults Study Protocol Completion of Study Protocol
- Primary Outcome Measures
Name Time Method Maximal rate of whole-body fat oxidation (mg/kg FFM/min) 7 - 14 days Fat free mass (FFM). Assessed during the incremental stage maximal cardio-respiratory fitness test
- Secondary Outcome Measures
Name Time Method Body fat localisation 1 day Assessed via a dual energy xray absorptiometry scan at Visit 4.
Skeletal Muscle sample (Optional) 1 day The optional muscle sample will be obtained from the quadriceps muscle using the Bergstrom technique on Visit 4.
Fasting pancreatic derived hormone concentrations (insulin and glucagon) 7-21 days Assessed via plasma sample extracted from the blood sample
Body Mass (kg) 7-21 days Assessed via body weighing scales
Maximal rate of whole-body fat oxidation (g/min) 7-14 days Non-adjusted rate. Assessed during the incremental stage maximal cardio-respiratory fitness test
Whole-body substrate oxidation rates (Carbohydrates and Lipid) during exercise 7 - 14 days Assessed during the incremental stage maximal cardio-respiratory fitness test via indirect calorimetry of expired gas samples.
Habitual Energy Expenditure / Physical Activity 7 - 21 days Physical activity will be measured by accelerometry and heart-rate monitoring for 7 days before each main trial day (Visit 2 and 3). This procedure will be explained by the CI. ntake can be calculated. The participants physical activity levels for the immediate 48-hrs prior to the beginning of each main trial (Visit 2 and 3) will be asked to be replicated as closely as possible.
Fasting lipid profiles (triglycerides / cholesterol) 7-21 days Assessed via serum sample extracted from the blood sample
Age 7-21 days Assessed via a participant questionnaire
Hip Circumference (cm) 7-21 days Assessed via use of an anthropometric tape measure
FATmax (% of maximum oxygen consumption) 7 - 14 days The exercise intensity that maximal rate of whole-body fat oxidation occurs at. Expressed as % of VO2peak). Assessed during the incremental stage maximal cardio-respiratory fitness test.
FATmax (% of Heart Rate max) 7 - 14 days The exercise intensity that maximal rate of whole-body fat oxidation occurs at. expressed either as % of heart rate max). Assessed during the incremental stage maximal cardio-respiratory fitness test
Smoking Status 7-21 days Assessed via a participant questionnaire
Dietary pattern / requirements (e.g. vegetarian, vegan, Celiac disease) 7-21 days Assessed via a participant questionnaire
Body fat percentage 7-21 days Bioelectrical Impedance Analysis from the body weighing scales
Lean body mass 1 day Assessed via a dual energy xray absorptiometry scan at Visit 4.
Adipose Tissue (Fat) sample (Optional) 1 day The optional fat sample will be obtained from the subcutaneous abdominal region (5 cm laterally of the umbilicus) via the 'lipoaspiration' technique on Visit 4.
FATmax (% of Watt max) 7 - 14 days The exercise intensity that maximal rate of whole-body fat oxidation occurs at. Expressed as % of Watt max). Assessed during the incremental stage maximal cardio-respiratory fitness test.
Whole-body substrate oxidation rates (Carbohydrates and Lipid) at rest 7 - 14 days Assessed at rest through the participant lying in a semi-supine position via indirect calorimetry of expired gas samples.
Resting metabolic rate 7 - 14 days Assessed at rest through the participant lying in a semi-supine position via indirect calorimetry of expired gas samples.
Self-reported Physical Activity level 7-21 days Assessed by the International Physical Activity Questionnaire (long form)
Fasting Adipose tissue derived hormone concentrations (leptin, adiponectin) 7-21 days Assessed via plasma sample extracted from the blood sample
Fasting catecholamine concentrations (epinephrine and norepinephrine) 7-21 days Assessed via plasma sample extracted from the blood sample
Fasting sex hormone concentrations (17 beta-estradiol, testosterone, progesterone) 7-21 days Assessed via serum sample extracted from the blood sample
Hydration Status (urine specific gravity) 7-21 days Assessed via analysis of urine sample with a refractometer
Ethnicity 7-21 days Assessed via a participant questionnaire
Medication / supplement use 7-21 days Assessed via a participant questionnaire
Cardiorespiratory fitness (VO2peak) 7 - 14 days Assessed during the incremental stage maximal cardio-respiratory fitness test
Habitual Energy Intake 7 - 21 days Participants will be asked to complete a self-weighed food and drink diary before each main trial day (Visit 2 and 3) so that average daily calorie and macronutrient intake can be calculated. The procedure will be explained by the CI. This diet monitoring period must include 3 week-days, at least one 1 weekend day and the immediate 48-hrs prior to the beginning of each main trial (Visit 2 and 3). Additionally, the prior 48-hrs before Visit 2 will be replicated before Visit 3.
Menstrual Cycle (females only) 7 - 21 days Assessed through a self-reported menstrual cycle questionnaire
Fasting glucose concentration 7-21 days Assessed via plasma sample extracted from the blood sample
Sex 7-21 days Assessed via a participant questionnaire
Body Mass Index (kg/m2) 7-21 days Assessed by dividing body weight in kg by height in metres squared.
Waist circumference (cm) 7-21 days Assessed via use of an anthropometric tape measure
Genotyping analysis 7 - 21 days Genotyping analysis will be assessed through the extraction of the buffy coat layer from the blood sample
Fat mass index (body fat in kg/m2) 7 - 21 days Assessed by dividing body fat in kg by height in metres squared.
Trial Locations
- Locations (1)
Department for Health, University of Bath
🇬🇧Bath, United Kingdom