Hypothesis:

1. What is the role of gut bacteria in body weight? Hypothesis: Alternation of gut microbiota composition has an influence on body weight by affecting energy disposal and storage in adipocytes, and gene expression involved in possessing components of diet. Wing Yin Cheung

2. BackGround: • The development of metabolic complications, associated with obesity during childhood, has repercussions in adulthood, increasing the risk of inflammatory disease, e.g. type 2 diabetes and CVD • Gut microbiota is an important factor in weight management by affecting • energy disposal and storage in adipocytes • involved in modulation of host immunity, and the inflammatory status associated with obesity in mice • gene expression involved in possessing components of diet

3. Research Paper Title: Interplay Between Weight Loss and Gut Microbiota Composition in Overweight Adolescents • Hypothesis • Calorie restriction and physical activity have a beneficial impact on gut microbiota composition related to body weight loss. People with higher weight loss may have greater amount of Lactobacillus and Bacteroides species, and lower amount of Clostridium species.

4. Design & Methods • Subjects • 36 adolescents (age  13-15 years) • 18 females & 18 males • Classified as overweight according to the International Obesity Task Force BMI criteria • BMI z-scores were calculated as a function of the subject’s obesity degree when compared with BMI local reference standards. • All anthropometric variables were measured in order, 3 times and averaged + skin fold test • Duration  over 10 weeks • Fecal and DNA sample • Microbial analysis  quantitative real-time PCR • Specific primers targeting different bacterial genera and species were used to characterize the fecal microbiota • Dietary assessment • Food diary records (kept 72 hours  2 weekdays and 1 weekend day) before study and after intervention • Analyzed by Dietitian

5. Intervention • Based on energy restricted diet (10-40% reduction), according to both obesity degree and regular physical activity • 10% restriction  when subject had BMI between 0 and 2 s.d. above mean • 20% restriction  when subject had BMI between 2 and 3 s.d. above mean • 30% restriction  when subject had BMI between 3 and 4 s.d. above mean • 40% restriction  when subject had BMI > 4s.d. above the mean • Maximum energy intake • 1,800 kcal/day for females • 2,200 kcal/day for males • Physical activity • prescribe at least 1 hour of moderate-to-vigorous intensity 3 or 5 per week • Energy expenditure ranges from 15-23 kcal /kg of body weight per week

6. No significant differences in dietary intake between both groups • The subjects showed marked differences in weight loss after intervention, and accordingly • Subdivided into two groups: • Low weight loss group • ( < 2.0kg of weight loss, n=13) • Do Not showed significant BMI and BMI z-score reductions after intervention • High weight loss group • ( > 4.0kg of weight loss, n=23) • Showed significant BMI and BMI z-score reductions after intervention Results:

7. Daily energy and nutrient intake before (baseline) and after intervention Results :

8. Comparison between High & Low weight-loss group: • Similar types of gut microbiotawere found between the Low and High weight loss group. • In the Low weight-loss group • No significant differences / changes in gut bacteria composition before and after intervention • In the high weight-loss group, • Increased • B.fragilis • Lactobacillus • Decreased • C.coccoides • B.longum Results

9. RESULTS • In the whole adolescent population, • Increased : • Bacteroidesfragilis group • Lactobacillus group • Decreased: • Clostridium coccoides • Bifidobacteriumlongum • Bifidobacteriumadolescentis

10. Bacteria counts in fecal samples of low and high weight-loss groups of adolescents, before and after intervention

11. Figure : Correlations between fecal bacterial counts and weight loss after intervention in high weight=loss group of adolescents. Increased levels of Lactobacillus group significantly correlated with weight loss Opposite correlation was found in E.coli correlated with weight loss Increased levels of Bacteroidesgroup significantly correlated with weight loss

12. Strengths Limitations • Population : obese adolescents who represents high-risk population groups • Age group (13-15 years old) • Gender  18 males vs 18 females • Short Duration : 10 weeks • Sample size: No Power Calculations • No Control groups • At the beginning • Comparison group based on amount of weight loss after intervention • Limitations of food composition database and • Inherent limitation of dietary assessment in free living young populations • No further details are available according to other key nutrients that are proved to serve as substrate for gut microbiota

13. My Conclusion • Both reduction in energy intake + increase in energy expenditure have beneficial influence on composition of gut microbiota of overweight adolescents related to weight loss • changes in composition of gut microbiota regulating body weight • Increase beneficial gut bacteria  promote gut health  reduce risk of inflammatory disease • Due to kcal restriction, • certain food components which favor for specific types of gut microbiota may be affected  affect gut bacteria counts after intervention • Based on the research results • higher weight loss  beneficial impact on certain bacterial population (such as B.fagilis) and harmful effect on other bacterial population (such as C.coccoides) • Low weight loss  no significant difference in bacterial population before and after intervention • Greater Weight-Loss  Greater benefits (Favors the growth of beneficial gut microbiota)

14. Suggestion for further studies : • Find out associations between composition of gut microbiota and certain food group • E.g. fat-restricted low calorie diet • E.g. CHO-restricted low calorie diet • find out what other key nutrients that are proved to serve as substrate for gut microbiota and how they have influence on levels of different gut microbiota population • E.g. Food with high PUFA • Long-term studies instead of short-term studies

15. References Santacruz A, Sanz Y, Marcos A, Warnberg J, Marti A, Martin-Matillas M, Campoy C, Moreno L, Veiga O, Redondo-Figuero C, Garagorri J, Azcona C, Delgado M, Garcia-Fuentes M, Collado M. Interplay between weight loss and gut microbiota composition in overweight adolescents. Obesity 2009;1710:1906-1915. doi:10.1038/oby.2009.112