Is fast­ing a long-ig­nored health sav­ior for di­a­bet­ics or a pos­si­ble cause?

Newsweek - - News - BY JES­SICA WAP­NER @jes­si­cawap­ner

Fast­ing and Di­a­betes. Plus: How Much Ex­er­cise Does It Take to Keep a Heart Strong?

weight gain may be driven by not only what we eat but also our ten­dency to eat all day long. That’s the think­ing be­hind the weight-loss trend of in­ter­mit­tent fast­ing, which has grown in pop­u­lar­ity in the past few years. An in­creas­ing num­ber of health pro­fes­sion­als are also pre­scrib­ing fast­ing to peo­ple with type 2 di­a­betes, which cur­rently af­flicts more than 29 mil­lion peo­ple in the United States. Yet a recent study warns that go­ing for long stretches with­out eat­ing could cause the very dam­age it’s sup­posed to pre­vent.

Type 2 di­a­betes is trig­gered in part by un­healthy eat­ing, which ren­ders the body re­sis­tant to in­sulin, a hor­mone pro­duced by the pan­creas. With­out in­sulin, sugar from food can’t en­ter our cells, leav­ing the blood with an ex­cess amount of sugar. At first, the pan­creas com­pen­sates by mak­ing more in­sulin, but even­tu­ally the de­mand wears it out. Di­a­bet­ics then be­come de­pen­dent on in­sulin in­jec­tions to con­trol their blood sugar.

Dr. Ja­son Fung is con­vinced that fast­ing un­does that cy­cle: Not eat­ing, af­ter all, re­duces blood sugar. And, as he points out, it’s some­thing we nat­u­rally do al­ready, when we sleep. “It’s sup­posed to be part of ev­ery­day life,” says Fung, a kid­ney spe­cial­ist who co-founded the Toronto-based In­ten­sive Di­etary Man­age­ment Pro­gram and wrote The Obe­sity Code and The Com­plete Guide to Fast­ing. Fast­ing can also send the body into ke­to­sis, in which it burns fat rather than sugar. That helps with los­ing weight, which also aids in slow­ing di­a­betes.

Sev­eral recent stud­ies sup­port this think­ing. Re­search pub­lished June 5 in the sci­en­tific jour­nal Cell Me­tab­o­lism found that eat­ing only be­tween 8 a.m. to 2 p.m.—in­stead of the more com­mon 8 a.m. to 8 p.m.—helped peo­ple with early signs of di­a­betes re­spond bet­ter to their body’s nat­u­ral in­sulin. The sched­ule also re­duced blood pres­sure and ap­petite, two fac­tors that worsen di­a­betes.

But some re­searchers are call­ing for cau­tion, in­clud­ing Ana Bonassa, from the Univer­sity of São Paulo, in Brazil. She and her col­leagues pre­sented a study in which rats sub­jected to in­ter­mit­tent fast­ing showed an in­crease in fat tis­sue, with dam­age to in­sulin-re­leas­ing cells in the pan­creas. Those ef­fects, Bonassa says, “could lead to di­a­betes and se­ri­ous health is­sues.” Fung dis­putes the re­sult. As with all an­i­mal-based clin­i­cal re­search, it isn’t nec­es­sar­ily ap­pli­ca­ble to men and women. Fur­ther­more, hu­mans have gone for long pe­ri­ods with­out eat­ing for most of our his­tory. “If fast­ing gives us di­a­betes,” he says, “then cave­men should have had a lot of it.”

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