From Science Daily, 23 Feb 2017
People who suffer long-term stress (such as those in poverty, according to epidemiologists Pickett and Wilkison) may also be more prone to obesity, according to research by scientists at UCL which involved examining hair samples for levels of cortisol, a hormone which regulates the body’s response to stress.
The paper, published in the journal Obesity, showed that exposure to higher levels of cortisol over several months is associated with people being more heavily, and more persistently, overweight.
Chronic stress has long been hypothesised to be implicated in obesity — people tend to report overeating and ‘comfort eating’ foods high in fat, sugar and calories in times of stress, and the stress hormone cortisol plays an important role in metabolism and determining where fat is stored.
Previous studies looking at the link between cortisol and obesity relied mainly on measurements of the hormone in blood, saliva or urine which may vary according to the time of day and other situational factors. These studies failed to capture long-term cortisol levels.
This research involved 2,527 men and women aged 54 and older taking part in the English Longitudinal Study of Ageing, taking data over a four-year period.
In the research, the scientists took a lock of hair 2cm long from each participant which was cut as close possible to a person’s scalp — this represented approximately two months’ hair growth with associated accumulated levels of cortisol. They also examined the participants’ weight, body mass index and waist circumference and how hair cortisol related to the persistence of obesity over time.
They found that people who had higher levels of cortisol present in their hair tended to have larger waist circumference measurements, were heavier, and had a higher body mass index (BMI). Individuals classified as obese on the basis of their BMI (greater than or equal to 30) or waist circumference (greater than or equal to 102cm in men, 88cm in women) had particularly high levels of hair cortisol.
“These results provide consistent evidence that chronic stress is associated with higher levels of obesity,” said Dr Sarah Jackson (UCL Epidemiology and Public Health) who led the research. “People who had higher hair cortisol levels also tended to have larger waist measurements, which is important because carrying excess fat around the abdomen is a risk factor for heart disease, diabetes, and premature death.”
“Hair cortisol is a relatively new measure which offers a suitable and easily obtainable method for assessing chronically high levels of cortisol concentrations in weight research and may therefore aid in further advancing understanding in this area.”
There were limitations to the study, which included the fact the data was from an older population in which levels of cortisol may differ relative to younger adults and the sample was almost exclusively white. It is not currently known whether chronically elevated cortisol levels are a cause or a consequence of obesity.
More research is needed and if causation is proved, then targeting cortisol levels may offer a new method for treating obesity.
Journal Reference: Sarah E. Jackson, Clemens Kirschbaum, Andrew Steptoe. Hair cortisol and adiposity in a population-based sample of 2,527 men and women aged 54 to 87 years. Obesity, 2017; 25 (3): 539 DOI: 10.1002/oby.21733
When Many Lack Affordable Healthy Meal Alternatives, It’s Important to Consider that a single high-fat meal can damage the metabolism
The global proliferation of overweight and obese people and people with type 2 diabetes is often associated with the consumption of saturated fats. Scientists at the German Diabetes Center (Deutsches Diabetes-Zentrum, DDZ) and the Helmholtz Center in Munich (HMGU) have found that even the one-off consumption of a greater amount of palm oil reduces the body’s sensitivity to insulin and causes increased fat deposits as well as changes in the energy metabolism of the liver. The results of the study provide information on the earliest changes in the metabolism of the liver that in the long term lead to fatty liver disease in overweight persons as well as in those with type 2 diabetes.
In the current issue of the Journal of Clinical Investigation, DZD researchers working at the German Diabetes Center, in conjunction with the Helmholtz Center in Munich and colleagues from Portugal, published a scientific investigation conducted on healthy, slim men, who were given at random a flavored palm oil drink or a glass of clear water in a control experiment. The palm oil drink contained a similar amount of saturated fat as two cheeseburgers with bacon and a large portion of French fries or two salami pizzas. The scientists showed that this single high-fat meal sufficed to reduce the insulin action, e.g. cause insulin resistance and increase the fat content of the liver. In addition, changes in the energy balance of the liver were proven. The observed metabolic changes were similar to changes observed in persons with type 2 diabetes or non-alcoholic fatty liver disease (NAFLD). NAFLD is the most common liver disease in the industrial nations and associated with obesity, the so-called “metabolic syndrome,” and is associated with an increased risk in developing type 2 diabetes. Furthermore, NAFLD in advanced stages can result in severe liver damage.
“The surprise was that a single dosage of palm oil has such a rapid and direct impact on the liver of a healthy person and that the amount of fat administered already triggered insulin resistance,” explained Prof. Dr. Michael Roden, scientist, Managing Director and Chairman at the DDZ and the German Center for Diabetes Research (Deutsches Zentrum für Diabetesforschung, DZD). “A special feature of our study is that we monitored the liver metabolism of people with a predominantly non-invasive technology, e.g. by magnetic resonance spectroscopy. This allows us to track the storage of sugar and fat as well as the energy metabolism of the mitochondria (power plants of the cell).” Thanks to the new methods of investigation, the scientists were able to verify that the intake of palm oil affects the metabolic activity of muscles, liver and fatty tissue. The induced insulin resistance leads to an increased new formation of sugar in the liver with a concomitant decreased sugar absorption in the skeletal muscles — a mechanism that makes the glucose level rise in persons afflicted with type 2 diabetes and its pre-stages. In addition, the insulin resistance of the fatty tissue causes an increased release of fats into the blood stream, which in turn continues to foster the insulin resistance. The increased availability of fat leads to an increased workload for the mitochondria, which can in the long term overtax these cellular power plants and contribute to the emergence of a liver disease.
The team of Prof. Roden suspects that healthy people, depending on genetic predisposition, can easily manage this direct impact of fatty food on the metabolism. The long-term consequences for regular eaters of such high-fat meals can be far more problematic, however.
Elisa Álvarez Hernández, Sabine Kahl, Anett Seelig, Paul Begovatz, Martin Irmler, Yuliya Kupriyanova, Bettina Nowotny, Peter Nowotny, Christian Herder, Cristina Barosa, Filipa Carvalho, Jan Rozman, Susanne Neschen, John G. Jones, Johannes Beckers, Martin Hrabě de Angelis, Michael Roden. Acute dietary fat intake initiates alterations in energy metabolism and insulin resistance. Journal of Clinical Investigation, 2017; 127 (2): 695 DOI: 10.1172/JCI89444
Deutsches Zentrum fuer Diabetesforschung DZD. “Pizza, burgers and the like: A single high-fat meal can damage the metabolism.” ScienceDaily. ScienceDaily, 16 February 2017. <www.sciencedaily.com/releases/2017/02/170216143956.htm>.