Cut­ting carbs in­stead of calo­ries keeps weight off, study says

The Tribune (SLO) (Sunday) - - Living - BY NARA SCHOENBERG

In a study of over­weight peo­ple main­tain­ing weight loss, those on a low-car­bo­hy­drate diet burned about 250 more calo­ries per day than those on a high­car­bo­hy­drate diet.

The study of 164 peo­ple, pub­lished re­cently by The BMJ med­i­cal jour­nal, notes the chal­lenge of main­tain­ing weight loss in the face of the re­sult­ing hunger and me­tab­o­lism slow­down, and says that the calo­rie-burn­ing ef­fect of a low-carb diet “may im­prove the suc­cess of obe­sity treat­ment.”

“These find­ings show that all calo­ries are not alike to the body, and that re­strict­ing car­bo­hy­drates may be a bet­ter strat­egy for long-term weight loss than re­strict­ing calo­ries,” said study co-au­thor Dr. David Lud­wig, co-di­rec­tor of the New Bal­ance Foun­da­tion Obe­sity Pre­ven­tion Cen­ter at Bos­ton Chil­dren’s Hos­pi­tal.

The study ad­dresses one of the most vex­ing prob­lems in weight loss: As the weight comes off, the body fights back, burn­ing fewer calo­ries and bom­bard­ing us with hunger sig­nals.

“It’s a recipe for fail­ure,” Lud­wig said.

It’s also some­thing of a mys­tery: Why does the body re­act as if it’s starv­ing when it clearly is not? For some re­searchers, in­clud­ing Lud­wig, the an­swer lies in the car­bo­hy­drate-in­sulin model, the the­ory that pro­cessed car­bo­hy­drates such as white bread trig­ger hor­monal changes that lead to hunger, metabolic slow­down and weight gain.

Pro­cessed car­bo­hy­drates di­gest quickly into sugar, rais­ing in­sulin lev­els, Lud­wig said. In­sulin, in turn, pro­grams fat cells to store ex­cess calo­ries. When calo­ries are locked up in fat cells, the brain can’t per­ceive them and thinks the body needs more food.

The au­thors of the study col­lab­o­rated with Fram­ing­ham State Uni­ver­sity, where 164 over­weight peo­ple – stu­dents, staff, fac­ulty and com­mu­nity mem­bers – agreed to eat only study-sup­plied food. First, study par­tic­i­pants lost about 12 per­cent of their body weight, roughly 20 to 25 pounds for the av­er­age par­tic­i­pant.

“We know that’s go­ing to stress their me­tab­o­lism,” Lud­wig said.

Then for the 20-week test phase, study par­tic­i­pants were ran­domly placed in three groups: those who ate di­ets com­posed of 20 per­cent car­bo­hy­drates, 40 per­cent, or 60 per­cent. Each diet con­tained 20 per­cent pro­tein, with the re­main­ing por­tion com­posed of fat. Di­ets used healthy foods and were as sim­i­lar as pos­si­ble, Lud­wig said. The goal at this stage was to main­tain the weight loss, not to lose any more weight.

Those on the low-carb diet burned 209 to 278 more calo­ries per day than those on the high-carb diet, a dif­fer­ence that would lead to an es­ti­mated 22-pound weight loss over three years if re­searchers weren’t in­ter­ven­ing to main­tain weight.

And the ef­fect was even larger for those who pro­duced high lev­els of in­sulin in re­sponse to car­bo­hy­drates; they burned 308 to 478 more calo­ries a day on the low-carb diet than they did on the high-carb diet.

How do you know if you’re a high in­sulin se­creter? “Look in the mir­ror,” Lud­wig ad­vised. “If your fat dis­tri­bu­tion is pre­dom­i­nantly around the mid­sec­tion – so you are more like an ap­ple than a pear – you’re more likely to be a high in­sulin se­creter.”

Phys­i­cal ac­tiv­ity lev­els were very sim­i­lar for the three diet groups be­fore the study be­gan, Lud­wig said.

The re­searchers en­cour­aged all par­tic­i­pants to main­tain their usual level of phys­i­cal ac­tiv­ity, which was mon­i­tored. Dur­ing the study, the low-carb group showed a ten­dency to­ward more mod­er­ate-vig­or­ous phys­i­cal ac­tiv­ity, per­haps as a re­sult of the diet, Lud­wig said via email. But he em­pha­sized that ex­er­cise was only a mi­nor com­po­nent of the to­tal ef­fect on calo­ries burned.

A co-au­thor of a 2015 PloS One jour­nal ar­ti­cle com­par­ing low-fat and low-carb di­ets praised the pre­ci­sion and de­sign of the new study, in­clud­ing the di­rect cal­cu­la­tion of en­ergy ex­pen­di­ture, which is dif­fi­cult and la­bor in­ten­sive.

“I think they brought a level of so­phis­ti­ca­tion that you don’t tend to see in these kinds of tri­als,” said Dr. Jonathan Sack­ner-Bern­stein, a for­mer Food and Drug Ad­min­is­tra­tion as­so­ciate cen­ter di­rec­tor for tech­nol­ogy and in­no­va­tion who does con­sult­ing for drug and de­vice com­pa­nies.

Sack­ner-Bern­stein said the study re­in­forced his be­lief that the more sen­si­tive you are to car­bo­hy­drates, in terms of your in­sulin re­sponse, the more im­por­tant it is to be on a car­bo­hy­drate-re­stricted diet.

Lud­wig said the study’s find­ings are very close to what the au­thors pre­dicted, but more work needs to be done.

“This is one study, so the find­ings need to be repli­cated and ex­am­ined in a broader pop­u­la­tion – al­though we did have quite a de­mo­graphic va­ri­ety in our par­tic­i­pants,” he said. “We need to see how this ef­fect might play out in other stud­ies, how other pop­u­la­tions would re­spond.”

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