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A new way to lose weight?

March 28, 2013
Courtesy of Harvard University
and World Science staff

Sci­en­tists may have new hope for an­y­one who’s tried to fight the bat­tle of the bulge. A study has found that mice quick­ly lose weight when im­planted with gut mi­crobes from oth­er mice that have un­der­gone gas­tric by­pass sur­gery.

The re­search­ers, from Har­vard Uni­vers­ity and Mas­sa­chu­setts Gen­er­al Hos­pi­tal, found these gut mi­crobes un­dergo dras­tic changes af­ter the sur­gery, equi­va­lent to hu­man “stomach stap­ling.” The next step was to trans­plant the lit­tle or­gan­isms into mice with germ-free gas­tro­intest­i­nal systems. 

The study is de­scribed in a March 27 pa­per in the jour­nal Sci­ence Trans­la­t­ional Med­i­cine.

“Simply by col­o­niz­ing mice with the al­tered mi­cro­bi­al com­mun­ity, the mice were able to main­tain a low­er body fat, and lose weight – about 20 per­cent as much as they would if they un­der­went sur­gery,” said Pe­ter Turn­baugh of Har­vard, one of two sen­ior au­thors of the pa­per.

The study re­sults may have ac­tu­ally un­der­es­ti­mated the ef­fect, he added.

“In some ways we were bi­as­ing the re­sults against weight loss,” Turn­baugh said, ex­plain­ing that the mice used in the study had­n’t been giv­en a high-fat, high-sugar di­et to in­crease their weight be­fore­hand. “The ques­tion is wheth­er we might have seen a stronger ef­fect if they were on a dif­fer­ent di­et.”

“Our study sug­gests that the spe­cif­ic ef­fects of gas­tric by­pass on the mi­cro­biota [gut mi­crobes] con­trib­ute to its abil­ity to cause weight loss and that find­ing ways to ma­ni­pu­late mi­cro­bi­al popula­t­ions to mim­ic those ef­fects could be­come a valua­ble new tool to ad­dress obes­ity,” said Lee Kap­lan, di­rec­tor of the Obes­ity, Me­tab­o­lism and Nu­tri­tion In­sti­tute at the hos­pi­tal and the pa­per’s oth­er sen­ior au­thor.

“We need to learn a good deal more about the mech­a­nisms by which a mi­cro­bi­al popula­t­ion changed by gas­tric by­pass ex­ert its ef­fects, and then we need to learn if we can pro­duce these ef­fects – ei­ther the mi­cro­bi­al changes or the as­so­ci­at­ed met­a­bol­ic changes – with­out sur­gery,” Kap­lan added.

Turn­baugh warned that it may be years be­fore the effects could be rep­li­cat­ed in hu­mans, and that such mi­cro­bi­al changes should­n’t be viewed as a way to lose those stub­born last 10 pounds with­out go­ing to the gym. Rath­er, the tech­nique may one day of­fer hope to dan­ger­ously obese peo­ple who want to lose weight with­out the trau­ma of sur­gery.

“It may not be that we will have a mag­ic pill that will work for eve­ry­one who’s slightly over­weight,” he said. “But if we can, at a min­i­mum, pro­vide some al­ter­na­tive to gas­tric by­pass sur­gery that pro­duces si­m­i­lar ef­fects, it would be a ma­jor ad­vance.”

“We think such stud­ies will al­low us to un­der­stand how host/mi­cro­bi­al in­ter­ac­tions in gen­er­al can in­flu­ence the out­come of a giv­en di­et,” Kap­lan added. “To some de­gree, what we’re learn­ing is a com­fort for peo­ple who have an is­sue with their weight, be­cause more and more we’re learn­ing that the sto­ry is more com­pli­cat­ed than just how much you ex­er­cise and how much you eat.”


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Scientists may have new hope for anyone who’s tried to fight the battle of the bulge. A study has found that mice rapidly lose weight when implanted with gut microbes from other mice that have undergone gastric bypass surgery. The researchers, from Harvard University and Massachusetts General Hospital, found these gut microbes undergo drastic changes after the surgery, so the next step is simply to transfer the organisms into sterile mice. The study is described in a March 27 paper in the journal Science Translational Medicine. “Simply by colonizing mice with the altered microbial community, the mice were able to maintain a lower body fat, and lose weight – about 20% as much as they would if they underwent surgery,” said Peter Turnbaugh of Harvard, one of two senior authors of the paper. The study results may have actually underestimated the effect, he added. “In some ways we were biasing the results against weight loss,” Turnbaugh said, explaining that the mice used in the study hadn’t been given a high-fat, high-sugar diet to increase their weight beforehand. “The question is whether we might have seen a stronger effect if they were on a different diet.” “Our study suggests that the specific effects of gastric bypass on the microbiota [gut microbes] contribute to its ability to cause weight loss and that finding ways to manipulate microbial populations to mimic those effects could become a valuable new tool to address obesity,” said Lee Kaplan, director of the Obesity, Metabolism and Nutrition Institute at the hospital and the other senior author of the paper. “We need to learn a good deal more about the mechanisms by which a microbial population changed by gastric bypass exert its effects, and then we need to learn if we can produce these effects – either the microbial changes or the associated metabolic changes – without surgery,” Kaplan added. “The ability to achieve even some of these effects without surgery would give us an entirely new way to treat the critical problem of obesity, one that could help patients unable or unwilling to have surgery.” While the results were exciting, Turnbaugh warned that it may be years before they could be replicated in humans, and that such microbial changes shouldn’t be viewed as a way to lose those stubborn last 10 pounds without going to the gym. Rather, the technique may one day offer hope to dangerously obese people who want to lose weight without going through the trauma of surgery. “It may not be that we will have a magic pill that will work for everyone who’s slightly overweight,” he said. “But if we can, at a minimum, provide some alternative to gastric bypass surgery that produces similar effects, it would be a major advance.” “We think such studies will allow us to understand how host/microbial interactions in general can influence the outcome of a given diet,” Kaplan added. “To some degree, what we’re learning is a comfort for people who have an issue with their weight, because more and more we’re learning that the story is more complicated than just how much you exercise and how much you eat.”