The “Iceman” or “Ötzi” refers to an individual whose mummy was found about 10 years ago in the receding glaciers of the Ötztal Alps a mountain range in the central Alps between Austria and Italy. His well preserved body has been stored in a cooling chamber of the Archeology Museum in Bolzano, Italy, and is probably the most thoroughly investigated individual from the Neolithic period. Can the stomach contents of this individual reveal something about the preferred diet of people transitioning from a hunter gatherer to an agrarian lifestyle, and the associated health benefits? To answer this question, investigators have examined the stomach contents of this 5,300-year old European glacier mummy who according to the latest forensic studies was killed by an arrow shortly after enjoying his last meal. The study revealed that the Iceman had a remarkably high proportion of fat in his diet, supplemented with fresh or dried wild meat and ancient grains. An earlier study had demonstrated that the gut microbial composition of the Iceman was more similar to microbiomes of agrarian societies (and of primates), suggesting a predominantly plant based diet with an occasional treat of wild game. Do we have any evidence for the health benefits of this ancient diet? The investigators were surprised of the large amount of animal fat found in the person’s stomach. The investigators asked: “Did he load up on fatty meat to meat the caloric needs of roaming in the extreme alpine environment in which he lived and where he was found at 3,210m above sea level?” On the other hand, the intake of animal adipose tissue fat has a strong correlation with increased risk of coronary artery disease. There was evidence on computer tomographic scans of the Iceman that he had major calcifications of his major blood vessels consisting with advanced atherosclerotic disease state, a surprising finding in an individual who likely got regular vigorous workouts climbing up and down the mountains in his backyard. He was in his 40s, the average life expectancy of people of his time, half of our current life expectancy. Obviously, the study only provides a snapshot of dietary habits of this time, and tells us little about the average intake of different types of food and the relative proportion of carbs, protein and fat. However, in view of the presence of grains and carbohydrates in his stomach and the composition of his gut…

Obesity and compromised metabolic health are often thought to be closely linked. However, a study by Fredrik Baeckhed’s group at the University of Gothenburg suggests that this is not necessarily the case – at least in brown bears! (1) By studying body weight and the gut microbiota in brown bears both during the summer and during the winter period - when these animals go into a 6 months hibernation period - they identified major differences in the diversity and relative abundances of certain gut microbiota. During the summer the bears overeat and dramatically gain body weight, while during the prolonged fasting period in winter they lose all the excess weight. The most fascinating aspect of this study was that despite their “summer obesity” the bears did not develop the negative metabolic changes including insulin resistance and diabetes known as metabolic syndrome, a metabolic dysregulation which has shown a dramatic increase in North America and other developed countries. Looking for a possible role of the gut microbiome in these seasonal metabolic changes, the investigators looked at the bears’ gut microbes and metabolites. Surprisingly, during hibernation there was a reduction in diversity and reduced levels of certain taxa, in particular Firmicutes and Actinobacteria, and increased levels of Bacteroidetes. Transfer of the stool of bears obtained during different seasons into germ free mice (mice without their own gut microbiome) mimicked some of the metabolic findings of the bears, clearly implicating a role of the microbiome in the seasonal metabolic variations. The three microbial taxa that showed seasonal variations in the bears make up the majority of the human gut microbiota, and changes in their relative abundance in the gut have previously been shown by Ruth Ley and coworkers in obese subjects. (2) In their study, they found that the relative abundance of Bacteroidetes increases while that of Firmicutes decreases as obese individuals lose weight on either a fat- or a carbohydrate-restricted low-calorie diet. The increase in Bacteroidetes was significantly correlated to weight loss but not to total caloric intake. In a study by Peter Turnbaugh and coworkers, the investigators showed that when ‘obese microbiota’ were transplanted into the gut of mice without their own microbiota (so called germ free mice) they showed a significantly greater increase in total body fat than mice colonized with the ‘lean microbiota’. Their results suggested that an “obese microbiome” has an increased capacity to harvest energy from the…