Plain English Summary
Background and study aims
The obesity epidemic worldwide is fast increasing and affecting individuals of all ages, races and both genders. It is related with a series of other issues including diabetes, hypertension, cancer and cardiovascular diseases. Obesity is caused by genetic and environmental factors such as over-consumption of energy and sedentary lifestyle. Of genetic variants, fat mass and the obesity associated gene (FTO) have been found to be consistently associated with obesity traits in several populations. However there is increasing interest in finding out whether lifestyle factors modify the association of FTO variants and obesity as this could better provide insight into the role of diet/environmental factors in obesity. The Mediterranean diet is a diet that is high in vegetables, olive oil and fish (lean sources of protein). A higher adherence to the Mediterranean dietary pattern (Med Diet) using Mediterranean diet scores (MDS) has been associated with a decrease in obesity, regardless of genetic risk. This study uses participants in the Tehran Lipid and Glucose Study (TLGS). The TLGS is a large-scale, community-based, prospective study being performed on a sample of residents of District 13 of Tehran, capital of Iran. The first phase of the TLGS was conducted from 1999 to 2001 and follow-up examinations have been conducted every 3 years (2002–2005; 2006–2008; 2008–2011, and 2011–2014) to identify newly developed diseases. The aim of this study is to investigate whether Med Diet could interact with FTO in relation to obesity among adult participants in order to identify environmental interactions to create preventive approaches in individuals with greater genetic susceptibility to obesity.
Who can participate?
Adults aged 18 years and older.
What does the study involve?
Participants undergo a baseline survey. Those who are evaluated as obese are excluded. The other participants are followed and randomly selected for follow-up surveys.The surveys include questions about food frequency and types of food ingested in order to provide a MDS score to participants. Other measures such as physical activity, smoking, and other demographics are also assessed. DNA samples are provided by participants in order to identify their genetic risk.
What are the possible benefits and risks of participating?
Participants may help prevent obesity in those with FTO risk alleles. There are no risks with participating.
Where is the study run from?
This study is run by the Shahid Beheshti Univeristy of Medical Sciences (Iran) and the TLGS is performed on a sample of residents of District 13 of Tehran (Iran).
When is the study starting and how long is it expected to run for?
February 1998 to February 2017
Who is funding the study?
Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences (Iran)
Who is the main contact?
Parvin Mirmiran, Prof.
mirmiran@endocrine.ac.ir
Trial website
Contact information
Type
Scientific
Primary contact
Dr Firoozeh Hosseini-Esfahani
ORCID ID
http://orcid.org/0000-0002-9697-0081
Contact details
Nutrition and Endocrine Research Centre
Research Institute for Endocrine Sciences
Shahid Beheshti University of Medical Sciences
No.24
Arabi Street
Yemen Avenue
Chamran Highway
Tehran
1985717413
Iran
+98 212 243 2500
f.hosseini@sbmu.ac.ir
Type
Scientific
Additional contact
Prof Parvin Mirmiran
ORCID ID
http://orcid.org/0000-0003-2391-4924
Contact details
Nutrition and Endocrine Research Centre
Research Institute for Endocrine Sciences
Shahid Beheshti University of Medical Sciences
No.24
Arabi Street
Yemen Avenue
Chamran Highway
Tehran
1985717413
Iran
+98 212 243 2500
mirmiran@endocrine.ac.ir
Additional identifiers
EudraCT number
ClinicalTrials.gov number
Protocol/serial number
Research Institute for Endocrine Sciences (Grant No. 840), Shahid Beheshti University of Medical Sciences
Study information
Scientific title
Mediterranean dietary pattern adherence modify the association between FTO genetic variations and obesity phenotypes
Acronym
Study hypothesis
Can Mediterranean Diet interact with FTO gene polymorphisms (rs1121980, rs1421085, rs9939973, rs8050136, rs17817449 and rs3751812) in isolation or combined form (GRS) in relation to obesity phenotypes among participants of the Tehran Lipid and Glucose Study (TLGS)?
Ethics approval
Ethics committee of the Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, 10/01/1999, ref: 840
Study design
Observational-nested case-control study
Primary study design
Observational
Secondary study design
Nested case-control study
Trial setting
Community
Trial type
Other
Patient information sheet
Condition
Obesity
Intervention
Participants undergo a baseline survey. Those who are evaluated as obese are excluded. The other participants are followed and randomly selected for follow-up surveys between 2006-2008, 2008-2011 and 2011-2014. Each of these cases are individually paired and matched by age (plus or minus five years), sex and duration of follow-up with a random control from a population with normal body mass index. The duration of follow-up is from baseline to the follow up survey which marks the end of their participation in the study.
The survey that participants fill out assessed participants dietary intakes using a valid and reliable 168-item semi-quantitative food frequency questionnaire (FFQ) at baseline and follow up surveys. The Mediterranean dietary score is computed according to richopoulou et al. based on the following eight components: Legumes, vegetables, nuts and fruits, fish, and cereals intake; dietary ratio of monounsaturated fatty acid (MUFA) to saturated fatty acid (SFA); intake of dairy products, mostly in the form of cheese or yogurt and intakes of meat and poultry. The anthropometric, physical activity, smoking and the other demographic variables are assessed at baseline and follow-up surveys, DNA products of participants were genotyped and genetic risk score is computed.
The risk of obesity (odds ratio) of individuals with different genetic risk scores assessed across the Mediterranean dietary score quartiles from baseline to follow-up survey.
Intervention type
Other
Phase
Drug names
Primary outcome measures
1. Weight is measured using the digital scales at baseline and each follow-up examination (every three years)
2. Height is measured using a tape measure at baseline and each follow-up examination (every three years)
3. Waist circumference is measured using the upstretched tape meter at baseline and each follow-up examination (every three years)
4. Hip circumference is measured using the upstretched tape meter at baseline and each follow-up examination (every three years)
Secondary outcome measures
1. BMI (body mass index) is calculated by dividing weight in kilograms on height in meters squared baseline (kg/m2) at baseline and each follow-up examination (every three years)
2. WHR (waist to hip ratio) is calculated by dividing waist on hip circumferences at baseline and each follow-up examination (every three years)
3. Obesity was defined as a BMI ≥30 kg/m2
4. BMI between 18.5 and 24.9 classified a person as having a normal weight
5. Waist circumference >95 cm for both genders was considered as indicators of abdominal obesity
6. WHR >0.8 in men and >0.9 in women, was considered as indicators of abdominal obesity
Overall trial start date
01/02/1998
Overall trial end date
15/02/2017
Reason abandoned
Eligibility
Participant inclusion criteria
1. Age ≥18 years
2. Both genders
3. Participating in baseline and follow-up examinations of Tehran Lipid and Glucose Study
4. BMI≥30 for cases, BMI≥18.5 and <25 for controls.
5. Not pregnant or lactating women
6. Not history of weight loss or gain >5 kg in the last 6 months
7. Not taking drugs that affect weight
8. Not under or over-reporters of energy intake
9. DNA purification in the range of 1.7<A260/A280<2
Participant type
Mixed
Age group
Adult
Gender
Both
Target number of participants
627 pairs of persons with obesity and their matched controls (1254 persons)
Participant exclusion criteria
1. Individuals with a history of weight loss or gain >5 kg in the last 6 months
2. Pregnant and lactating
3. Taken drugs that affect weight
4. Cases/controls lacking DNA purification in the range of 1.7<A260/A280<2
5. Reported energy intakes divided by the predicted energy intake did not qualify for the ±3SD range
Recruitment start date
31/01/1999
Recruitment end date
20/01/2015
Locations
Countries of recruitment
Iran
Trial participating centre
Shahid Beheshti University of Medical Sciences
Nutrition and Endocrine Research Center
Research Institute for Endocrine Sciences
No. 24, Arabi Street
Yemen Anenue
Chamran highway
Tehran
1985717413
Iran
Sponsor information
Organisation
Shahid Beheshti University of Medical Sciences
Sponsor details
Nutrition and Endocrine Research Centre
Research Institute for Endocrine Sciences
No. 24
Arabi Street
Yemen Avenue
Chamran Highway
Tehran
1985717413
Iran
+98 212 243 2500
mirmiran@endocrine.ac.ir
Sponsor type
Research organisation
Website
Funders
Funder type
Not defined
Funder name
Shahid Beheshti University of Medical Sciences
Alternative name(s)
SBUMS
Funding Body Type
government organisation
Funding Body Subtype
government non-federal
Location
Iran
Results and Publications
Publication and dissemination plan
Phase one and two have been published. The manuscript is planned to submit in American Journal of Clinical Nutrition as soon as we receive Clinical Trial Registration Number.
IPD sharing statement:
The datasets generated during and/or analysed during the current study are/will be available upon request from Dr. Amir-Abbas Momenan at momenan@gmail.com or momenan@endocrine.ac.ir
Intention to publish date
15/08/2017
Participant level data
Available on request
Results - basic reporting
Publication summary
2002 results (phase one) in https://www.ncbi.nlm.nih.gov/pubmed/12643001
2009 results (phase two) in in https://www.ncbi.nlm.nih.gov/pubmed/19166627