Research Group Members
Kirsi Pietiläinen

Principal Investigator Kirsi Pietiläinen is trained as an MD (specialist in Internal Medicine), PhD, and MSc in Nutrition. She was awarded tenure, thereby becoming Professor of Clinical Metabolism in January 2017 at the University of Helsinki, Faculty of Medicine.

Kirsi is passionate about the study of obesity, its pathophysiology and novel treatments. Her research is a joint effort of her two teams at the Obesity Research Unit (University of Helsinki) and the Obesity Centre (Helsinki University Hospital). Her lab was part of the Centre of Excellence for Research on Mitochondria, Metabolism and Disease of the Academy of Finland, Finmit, in 2014-2019, which serves as a foundation for her group’s research within the field of mitochondria.

As an MD, Kirsi aims to improve obesity treatment in Finland by delivering continuing education courses, by chairing the Clinical Guidelines for Management of Obesity, and most recently by spearheading a new web-based obesity treatment program (

Kirsi’s dedication to obesity research is also evident through numerous engagements in international collaborations and advisory boards.

View Kirsi in Research Portal

Bram Berntzen

Bram Berntzen is a postdoctoral researcher. He is interested in the genetic and behavioral associations with obesity. His research focuses on genetically identical twin pairs with large within-pair differences in body mass index (BMI). He currently investigates how the twins' acquired BMI is affected by their polygenic risk score of BMI and by their lifestyle behaviors, such as physical activity, eating behavior, and sleep.

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Tarja Hallaranta

Study nurse (Public health nurse)

Hanna Haltia

Hanna Haltia is an MD PhD student interested in mitochondria, metabolism and the way obesity remodels adipocyte function. Hanna's current research focuses on the relation of mitochondrial dysfunction in adipose tissue to low-grade chronic inflammation in obesity. In the future, she would like to contribute to finding better and more effective ways to treat obesity.


Sini Heinonen

Sini Heinonen is a postdoctoral researcher (PhD, MD, Resident in Internal Medicine). Sini has studied adipose tissue in obesity in identical obesity-discordant twins, with special interest in adipose tissue mitochondria and their relation to the metabolic complications of obesity, adipocyte size and inflammation. Her work has included the characterization of a healthy obese twin cohort, with no metabolic complications of obesity. Current interests also comprise the biogenesis and function of mitochondria in human adipose precursor cells and adipose tissue in conservative and bariatric surgery-induced weight loss. The aim is to characterize factors affecting low mitochondrial content and function in obesity and suggest strategies how the metabolic complications of obesity could possibly be reversed.

Dissertation: Adipose tissue metabolism in acquired obesity

View Sini in ResearchGate

Elena Herbers

Elena Herbers is a passionate PhD student about cell biology and metabolism. The main topic of Elena's research is to study mitochondrial functions in adipocytes and role of mitochondria in obesity and metabolic complications development. Do obese people have “lazy” mitochondria? Can we find a way to activate mitochondria in fat tissue? She is trying to answer these questions by working with cells and using various molecular biology techniques.

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Birgitta van der Kolk

Birgitta van der Kolk is a postdoctoral research fellow. Her multidisciplinary research concentrates on understanding biological pathways in inter-organ crosstalk involved in obesity and obesity-related metabolic diseases. Her work involves human (intervention) studies, including a range of in vitro experiments with stem cells derived from human adipose tissue and skeletal muscle. Her present research focuses on characterizing monozygotic twin pairs who are weight discordant in detail. Moreover, she studies the effects of different types of weight loss (e.g. diet and surgery) on adipose tissue metabolism.


Hanna Kukkonen

Biomedical Laboratory Scientist

Sakris Kupila

Sakris Kupila is an MD PhD student in Obesity Research Unit.

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Helena Lapatto

Helena Lapatto's PhD project concentrates on studying how obesity is related to the NAD+/Sirtuin metabolism. Surprisingly little is known about the sirtuin-related gene expression changes in human obesity, especially in the adipose tissue and adipocytes. The individual studies focus on different perspectives, ranging from epigenetics to therapy. Her research goal is to gain insight to the interaction between the cellular and clinical phenotype.


Simo Metsikkö

Research assistant (BSc in Molecular biosciences)

Maheswary Muniandy

Mahes Muniandy is a post-doctoral researcher who specializes in bioinformatics analysis of OMICS data. Her research in the field of obesity and weight loss focuses on statistical modelling of relationships between molecular-level data and obesity phenotypes. A considerable part of her research work involves scripting and statistical analysis using R; she is happiest when her research results reveal or confirm the biology of obesity and its related co-morbidities. Before starting her career in research, she worked for many years in telecommunications and, as a result, maintains a nostalgic interest in technology. 

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Emma Paasikivi

Biomedical Laboratory Scientist 

Sina Saari

Postdoctoral researcher Sina Saari's research interests lie in better understanding the metabolic role and regulation of mitochondria, and particularly in how the balance between the respiratory chain and the tricarboxylic acid cycle reflects on the metabolic state of the cell, tissues and eventually, the whole organism.

Lily Trei

Biomedical Laboratory Scientist