The Bugs in Your Guts Can Make you Fat: A Whole New Field of Research

September 26, 2006The Bugs in Your Guts Can Make you Fat: A Whole New Field of Research Competency # 1 Know Thyself Reference: Int J Obes (Lond). 2005 Mar;29(3):281-6 Once upon a time we said that you gained weight when you ate too much.  Energy in and out had to be equal.  Fair enough.  A calorie was a calorie.  Simple physics.  Then we found out that there were some genes that made some people more efficient at energy utilization. It turned out that the old formulas of how many calories you might need just weren’t right all the time.  We’ve now found about 50 genes that are involved with how we lay down extra fuel as fat instead of burning it as energy.  But conundrums still arose.  There continue to be cases of identical twins that weighed markedly different amounts. How to explain that?  Same genes?  Now we are beginning to learn and this is fascinating stuff.  Infectobiology, two lines of enquiry around the same idea.  The “germs” that we are “infected” with can have dramatic effects on our bodies that make our metabolisms efficient or not. First, the bacteria in your gut.  Recent research with germ free mice have shown that absolutely germ free baby mice grow up skinny and can’t gain weight until their guts get populated with the proper gut bacteria.  The bacteria you have in your intestine turn out to do several profoundly important things.  One of those bacteria called B. theta suppresses a protein called FIAF.  FIAF prevents you from storing fat.  The more you suppress FIAF, the easier to lay down fat.  Then there is the balance of Bacteroidetes to Firmicutes, the two main families of bacteria in your gut.  Turns out that if mice guts have more B than F, they are skinny.  But if they have more F than B, they are fat.   In humans at obesity clincs, stool samples of obese patients show the same trends. Then, there’s the adenovirus.  It often causes nasty sore throats, pink eye and some tummy virus, but one subtype infects and kills chickens.  When the chicken die, they have all sorts of fat in their abdomens, low cholesterol and low triglycerides.  Now, we humans get higher cholesterol and triglycerides as we get fatter so the chickens made for an interesting study.  It turns out other strains of adenovirus infected other mammals and all of them got fat compared to uninfected animals.  It’s considered unethical to infect humans to see if we can make them fat with a virus so we can only look with antibodies to see if populations have been infected.  Guess what happens when Dr. Atkinson and Dhurandhar from the University of Madison surveyed the blood of several hundred obese Wisconsin and Florida residents?  You’re right.  The obese volunteers showed a much higher rate of infection with adenovirus.  And for being overweight, they had lower cholesterol and triglycerides. WWW.  What Will Work for Me?  What does this all mean?  Of course a calorie is a calorie.  And each of us have to discover our own balance between what we eat and how much what we eat turns into fat.  That remains true.  And some of us have genes that are more efficient than others.  But we are now learning that the picture is much more complex.  It isn’t a level playing field.  Some of us have a balance of bacteria in our guts that make it easy to gain weight, compared to others.  Some of us may have been infected with a virus that changes the efficiency with which we store energy as fat.  Figuring out how these two ideas work and how we can manipulate them to our benefit will be a very interesting story.  It’s obviously a story at the very first chapter.  But if you feel like you can’t eat one calorie extra without gaining weight, you might, in fact be right.  If this were the ice age and your survival depended on having a very efficient metabolism, you’d be in a great spot.  In America in 2006, you really do have to be vigilant.

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