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You write: "Is everyone's digestive system, at all times and under all conditions, equally efficient at extracting energy from food?" The ability of people to

You write: "Is everyone's digestive system, at all times and under all conditions, equally efficient at extracting energy from food?" The ability of people to digest food is influenced by a number of factors including the amount of bacteria in their gut: http://linkinghub.elsevier.com/retrieve/pii/S026156149780252X http://linkinghub.elsevier.com/retrieve/pii/S026156149780252... "The human large intestine contains a microbiota, the components of which are generically complex and metabolically diverse. Its primary function is to salvage energy from carbohydrate not digested in the upper gut. This is achieved through fermentation and absorption of the major products, short chain fatty acids (SCFA), which represent 40–50% of the available energy of the carbohydrate. The principal SCFA, acetate, propionate and butyrate, are metabolized by the colonic epithelium (butyrate), liver (propionate) and muscle (acetate). Intestinal bacteria also have a role in the synthesis of vitamins B and K and the metabolism of bile acids, other sterols and xenobiotics. The colonic microflora are also responsive to diet. In the presence of fermentable carbohydrate substrates such as non-starch polysaccharides, resistant starch and oligosaccharides, bacteria grow and actively synthesize protein. The amount of protein synthesis and turnover within the large intestine is difficult to determine, but around 15 g biomass is excreted in faeces each day containing 1 g bacterial-N. Whether bacterially synthesized amino acids are ever absorbed from the colon remains unclear." Also: http://mic.sgmjournals.org/cgi/content/abstract/132/6/1647 http://mic.sgmjournals.org/cgi/content/abstract/132/6/1647 Also, there is the possibility that changing the bacteria can have positive results: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2672.1993.tb02790.x/abstract http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2672.1993.... On a personal note, having taken a lot of antibiotics, I can tell you that dramatic swings in weight are possible when you take antibiotics. And this is very important to consider: http://www.mayoclinicproceedings.com/content/83/4/460.full http://www.mayoclinicproceedings.com/content/83/4/460.full "Obesity results from alterations in the body's regulation of energy intake, expenditure, and storage. Recent evidence, primarily from investigations in animal models, suggests that the gut microbiota affects nutrient acquisition and energy regulation. Its composition has also been shown to differ in lean vs obese animals and humans. In this article, we review the published evidence supporting the potential role of the gut microbiota in the development of obesity and explore the role that modifying the gut microbiota may play in its future treatment. Evidence suggests that the metabolic activities of the gut microbiota facilitate the extraction of calories from ingested dietary substances and help to store these calories in host adipose tissue for later use. Furthermore, the gut bacterial flora of obese mice and humans include fewer Bacteroidetes and correspondingly more Firmicutes than that of their lean counterparts, suggesting that differences in caloric extraction of ingested food substances may be due to the composition of the gut microbiota. Bacterial lipopolysaccharide derived from the intestinal microbiota may act as a triggering factor linking inflammation to high-fat diet-induced metabolic syndrome. Interactions among microorganisms in the gut appear to have an important role in host energy homeostasis, with hydrogen-oxidizing methanogens enhancing the metabolism of fermentative bacteria. Existing evidence warrants further investigation of the microbial ecology of the human gut and points to modification of the gut microbiota as one means to treat people who are overweight or obese."

lkrubner 16y ago
Also, there is this, again, very important: http://rspb.royalsocietypublishing.org/content/early/2010/11/19/rspb.2010.1890.abstract?sid=bbc3ed30-1fc1-44c4-8d4d-41a6fac12c1e http://rspb.royalsocietypublishing.org/content/early/2010/11... "A dramatic rise in obesity has occurred among humans within the last several decades. Little is known about whether similar increases in obesity have occurred in animals inhabiting human-influenced environments. We examined samples collectively consisting of over 20 000 animals from 24 populations (12 divided separately into males and females) of animals representing eight species living with or around humans in industrialized societies. In all populations, the estimated coefficient for the trend of body weight over time was positive (i.e. increasing). The probability of all trends being in the same direction by chance is 1.2 × 10−7. Surprisingly, we find that over the past several decades, average mid-life body weights have risen among primates and rodents living in research colonies, as well as among feral rodents and domestic dogs and cats. The consistency of these findings among animals living in varying environments, suggests the intriguing possibility that the aetiology of increasing body weight may involve several as-of-yet unidentified and/or poorly understood factors (e.g. viral pathogens, epigenetic factors). This finding may eventually enhance the discovery and fuller elucidation of other factors that have contributed to the recent rise in obesity rates." My own guess is that some of the obesity epidemic can be explained by bacteria. This would either be a new strain of bacteria, or (more likely) an old one that has mutated due to the abundant supply of food that humans have been exposed to over the last 150 years. Likely this is a bacteria that has lived in the guts of mammals for a very long time, possibly millions of years. It is interesting to consider that, while a good deal of research has been done into how mammals react to famine, no research that I know of has been done into how the bacteria in our gut responds to our experience of famine. Or prolonged abundance. Of course, there are many novel factors in the environment today. Some chemical that effect our metabolism is also a possible explanation.

lkrubner 16y ago

Also, there is this, again, very important: http://rspb.royalsocietypublishing.org/content/early/2010/11/19/rspb.2010.1890.abstract?sid=bbc3ed30-1fc1-44c4-8d4d-41a6fac12c1e http://rspb.royalsocietypublishing.org/content/early/2010/11... "A dramatic rise in obesity has occurred among humans within the last several decades. Little is known about whether similar increases in obesity have occurred in animals inhabiting human-influenced environments. We examined samples collectively consisting of over 20 000 animals from 24 populations (12 divided separately into males and females) of animals representing eight species living with or around humans in industrialized societies. In all populations, the estimated coefficient for the trend of body weight over time was positive (i.e. increasing). The probability of all trends being in the same direction by chance is 1.2 × 10−7. Surprisingly, we find that over the past several decades, average mid-life body weights have risen among primates and rodents living in research colonies, as well as among feral rodents and domestic dogs and cats. The consistency of these findings among animals living in varying environments, suggests the intriguing possibility that the aetiology of increasing body weight may involve several as-of-yet unidentified and/or poorly understood factors (e.g. viral pathogens, epigenetic factors). This finding may eventually enhance the discovery and fuller elucidation of other factors that have contributed to the recent rise in obesity rates." My own guess is that some of the obesity epidemic can be explained by bacteria. This would either be a new strain of bacteria, or (more likely) an old one that has mutated due to the abundant supply of food that humans have been exposed to over the last 150 years. Likely this is a bacteria that has lived in the guts of mammals for a very long time, possibly millions of years. It is interesting to consider that, while a good deal of research has been done into how mammals react to famine, no research that I know of has been done into how the bacteria in our gut responds to our experience of famine. Or prolonged abundance. Of course, there are many novel factors in the environment today. Some chemical that effect our metabolism is also a possible explanation.