Low-carb vs. low-fat

New re­search says it doesn’t re­ally mat­ter

The Hamilton Spectator - - HEALTH - CAR­RIE DENNETT Car­rie Dennett is a reg­is­tered di­eti­tian nu­tri­tion­ist. Wash­ing­ton Post

For ev­ery pa­tient who comes to me be­liev­ing a low-carb diet is the way to be healthy or con­trol weight, I have an­other who has been un­able to shrug off the ves­tiges of the low­fat era, con­vinced that eat­ing more fat will lead to heart dis­ease or weight gain.

I re­mind them that the ev­i­dence strongly sug­gests that when you re­duce some­thing in your diet — such as carbs or fat — it’s im­por­tant to be mind­ful of what you re­place it with. For ex­am­ple, when the pub­lic was ad­vised to lower fat decades ago, most peo­ple swapped it for foods high in sugar and white flour, rather than with fruits, veg­eta­bles and whole grains. Not ideal.

When it comes to weight loss, the past sev­eral years of re­search show that low-carb di­ets may have a slight short-term edge on av­er­age, but that nei­ther can claim true su­pe­ri­or­ity, es­pe­cially given that about 95 per cent of di­eters end up re­gain­ing. A decade ago, a group headed by nu­tri­tion sci­en­tist Christo­pher Gard­ner, pro­fes­sor of medicine at Stan­ford Univer­sity, pub­lished a study com­par­ing the Atkins, Zone, Or­nish and LEARN di­ets among a group of 311 women. Af­ter a year, av­er­age weight loss was only a few pounds, but when you looked be­yond that, the dif­fer­ence be­tween losers and gain­ers on each of the four di­ets was huge: some lost 55 pounds, oth­ers gained 10 to 20 pounds. Why?

Gard­ner’s group de­cided to try to an­swer that ques­tion, fo­cus­ing not on which diet was best, but which diet was best for whom. Some pre­lim­i­nary re­search — in­clud­ing one study from Gard­ner’s group pub­lished in 2012 — sug­gested that how some­one’s body re­sponds to the hor­mone in­sulin may be key. And then there’s our in­di­vid­ual ge­netic makeup — could it pre­dis­pose us to thriv­ing on less fat or less carbs?

I had been look­ing for­ward to hear­ing the re­sults of Gard­ner’s more re­cent DIETFITS study at a con­fer­ence a few months ago. When I did, what first struck me was how rel­a­tively “real world” this study was, de­signed to help par­tic­i­pants stick to their ran­domly as­signed plan, while fol­low­ing it in a sus­tain­able way. I’ve had a few pa­tients who went on months-long food ben­ders af­ter par­tic­i­pat­ing in highly re­stric­tive diet stud­ies, so I con­sider “sus­tain­able” a crit­i­cal de­tail.

Be­cause there’s no stan­dard def­i­ni­tion of “low-fat” or “low-carb,” Gard­ner asked the 609 par­tic­i­pants to aim for 20 per cent carbs or fat, depend­ing on their diet as­sign­ment. Af­ter a few weeks, they could ad­just up­ward if needed. “Please help de­fine for the Amer­i­can pub­lic what is low-carb and low-fat, not just lower,” he said to them. “What’s the low­est you can tol­er­ate so you can look us in the eye and say, at the end of this pe­riod, ‘Yeah, I think that this place where I ended up is some­thing I could do for the rest of my life.’”

In the end, “low-carb” meant about 30 per cent carbs and 45 per cent fat, while “low-fat” was about 29 per cent fat and 48 per cent carbs. De­spite not be­ing re­quired to cut calo­ries, par­tic­i­pants were eat­ing an av­er­age of 500 calo­ries less, and what they were eat­ing was high qual­ity. The low-fat group was en­cour­aged to choose whole grains, a va­ri­ety of beans and lentils, sea­sonal or­ganic fruit, or­ganic low-fat milk and lean meats. The low-carb group was pointed to­ward high­qual­ity oils and fats, or­ganic av­o­ca­dos, hard cheeses, nut but­ters, grass-fed meat and pas­ture-raised eggs. “Ev­ery­one was sup­posed to have veg­eta­bles all day long as much as they could, have a salad ev­ery day, and no added sugar and as lit­tle re­fined flour as you could get,” Gard­ner said.

The par­tic­i­pants lost a cu­mu­la­tive 6,500 pounds, but Gard­ner and his team found that there was no dif­fer­ence be­tween low-carb and low-fat di­ets. The av­er­age weight loss for each group only dif­fered by about two pounds, and each group had in­di­vid­u­als who lost 65 pounds and oth­ers who gained 20 pounds. Nei­ther group had an ad­van­tage when it came to me­tab­o­lism slow­ing or fat loss vs. loss of lean mus­cle. The hy­poth­e­sis that peo­ple who had in­sulin re­sis­tance (cells that re­sist in­sulin’s cue to take up glu­cose from the blood­stream) would do best on the low-carb diet, while those who did not would do bet­ter on a low-fat diet. That turned out not to be uni­ver­sally true. There was no pat­tern based on ge­netic makeup, ei­ther. Anal­y­sis based on par­tic­i­pants’ gut mi­cro­bio­tas is pend­ing.

The take-away? Don’t pin your hopes on re­duc­ing fat or carbs. In­stead, con­sider this over­ar­ch­ing theme from the par­tic­i­pants who did best on ei­ther diet: “Re­gard­less of low-carb or low-fat, we helped them change their re­la­tion­ship to food,” Gard­ner said. “They didn’t eat in the car, they didn’t eat in the li­brary, they didn’t eat while they were walk­ing. They went to the farm­ers mar­ket more, they cooked more meals with their fam­ily.”

While you’re at it, think about what way of eat­ing will sat­isfy you. Gard­ner never asked par­tic­i­pants to cut calo­ries, but they did, over­all, and he thinks sa­ti­a­tion may be the key.

“Maybe the en­ergy deficit pre­scrip­tion makes them feel un­com­fort­able and chal­lenged and hun­gry,” he said.

“Maybe if you just say, ‘Eat as much as you want un­til you’re sa­ti­ated, but eat this way un­til you’re sa­ti­ated’ ... I’d re­ally like to look into that.”

They didn’t eat in the car, they didn’t eat in the li­brary, they didn’t eat while they were walk­ing. They went to the farm­ers mar­ket more, they cooked more meals with their fam­ily.

, GETTY

All study par­tic­i­pants were “sup­posed to have veg­eta­bles all day long as much as they could, have a salad ev­ery day, and no added sugar and as lit­tle re­fined flour as you could get,” nu­tri­tion sci­en­tist Christo­pher Gard­ner said.

Newspapers in English

Newspapers from Canada

© PressReader. All rights reserved.