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