How do Super Lean Subjects Keep Resistant to Body Weight Gain?

Study Overview
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Brief Summary
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Obesity is the 5th leading cause of global death, and is major risk factors for many chronic diseases, such as type 2 diabetes, cardiovascular diseases, hypertension and cancer. Obesity is caused by an imbalance between energy intake and energy expenditure, and it is widely agreed to be a consequence of a gene by environment interaction. Although on average obesity rates are increasing, the shape of the distribution of adiposity is changing: it is becoming more right skewed. This is because there is a population of very lean subjects that has remained almost unchanged by the epidemic. The investigators have called these very lean individuals that are resistant to the epidemic and sustain a BMI < 18.5 kg/m2 'super lean' subjects. We have very little understanding of the lifestyles of these individuals and how they are able to maintain their super lean phenotype, and whether the basis of their leanness is primarily genetics.

Detailed Description
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In this study, the investigators will recruit a sample of 150 super lean healthy volunteers with a BMI >15 and < 18.5 kg/m2 aged 20-40 years, in parallel with an age matched group of 150 healthy subjects with a BMI ≥22 and < 25 kg/m2 as the control group. The investigators will screen out any individuals with eating disorders. In both groups, the investigators will study their lifestyles in particular focusing on their physical activity patterns and their food intake choices (monitored via food intake diaries and supported by metabolomics analyses of their urine to detect biomarkers of different food groups). Saliva samples will be collected for genotyping. The investigators will SNP genotype the individuals for 30 known polymorphic loci previously linked to obesity to establish if they have a particular genetic profile linked to their lean phenotype.

Official Title
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The Investigation of Lifestyle and Genetics in Super Lean Subjects That Keep Them Resistant to Weight Gain

Conditions
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Thinness, Health Behavior, Genetics

Intervention / Treatment
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* Behavioral: Superlean


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: control: BMI 20-25 kg/m2, healthy, age 20-40 years old superlean: BMI 15-18 kg/m2, healthy, with no eating disorders and diabetes, age 20-40 years old Exclusion Criteria: Pregnant women and women in lactation Subjects are suffering from eating disorders or diabetes.

Ages Eligible for Study
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Minimum Age: 20 Years
Maximum Age: 40 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Control<br>20 kg/m2 ≤ BMI ≤ 25 kg/m2, healthy, with no eating disorder, 150 subjects, 20 - 40 years old | Behavioral: Superlean<br>* Behavioural data will be collected on all subjects in either control group or superlean group. Blood or saliva samples will be collected for DNA extraction and genotyping.<br>|
| Superlean<br>15 kg/m2 ≤ BMI ≤ 18 kg/m2, healthy, with no eating disorder, 150 subjects, 25 - 35 years old in particular | Behavioral: Superlean<br>* Behavioural data will be collected on all subjects in either control group or superlean group. Blood or saliva samples will be collected for DNA extraction and genotyping.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Anthropometric measurements of participants in both control and superlean groups | Height, waist and hip circumferences (cm) and body composition will be measured on arrival. | Through study completion, an average of 2 years | 
| Demographic characteristics of all participants in both control and superlean groups | Life style questionnaire filled out on arrival. | Through study completion, an average of 2 years |