The New En­durance Fuel


Men's Health (Singapore) - - PERSONAL TRAINER -

ZZach Bit­ter, an ac­com­plished en­durance ath­lete, sailed through the ini­tial 35 miles (56km) of his first ul­tra­ma­rathon, the 50-mile North Face En­durance Chal­lenge. He was en­er­gised and fo­cused. Fif­teen more miles – no sweat, he thought.

But then came hill af­ter hill, and by mile 40, he was run­ning on fumes and los­ing fo­cus. He rounded a cor­ner, started one more long, bru­tal climb… and suf­fered a loss in en­ergy.

He cursed him­self and the race route as he stag­gered into one of the last aid sta­tions. Soft drinks and sports drinks propped him up the rest of the way to­wards a less-than-smooth fin­ish.

Bit­ter com­peted in more ul­tras, but they al­ways ended the same way: He’d cruise his first 30 to 40 miles, and then in­evitably reach a point in the race that left him feel­ing light­headed and ir­ri­ta­ble, and strug­gling to push for­ward at an even pace.

In search of a so­lu­tion, he scru­ti­nised ev­ery as­pect of his train­ing and nu­tri­tion plan. He did re­search and asked ques­tions. Then he made a rad­i­cal change: He axed a ton of carbs from his diet, slashed his pro­tein in­take, and ate a lot more fat.

Af­ter eight weeks on the plan, Bit­ter’s train­ing in­ten­si­fied and his re­cov­ery times fell. In his next race, he didn’t suf­fer the same fate of his pre­vi­ous ul­tra­ma­rathon and went on to win four ul­tra­ma­rathons in 2012, break­ing the US record in 2013 and his own record in 2015.

Bit­ter’s eat­ing plan – low-carb, high-fat and mod­er­ate pro­tein – is called a ke­to­genic diet. It’s not for the faint of heart, and even though it goes against years of “carbs are king” en­durance dogma, it’s gain­ing trac­tion with some elite en­durance ath­letes, who say it helps them go harder for longer and feel just as good on their 50th mile as they did on their first. How could such a coun­ter­in­tu­itive plan pos­si­bly work?

Like this: With a typ­i­cal diet, your body con­verts glu­cose (a type of sugar) from the carbs you eat into glyco­gen. That glyco­gen is stored in your liver and mus­cles, where it’s a fast fuel for hard ex­er­cise. Un­for­tu­nately, how­ever, your body can store only enough glyco­gen for around two hours of in­tense ex­er­cise.

If you do only short events, that’s fine. But if you’re a dis­tance junkie, it’s a prob­lem. Once you hit hour 2 with­out re­fu­el­ing, your glyco­gen stores are tapped and your body searches for en­ergy else­where. Find­ing noth­ing, it crashes.

To pre­vent this, you pound gels, drinks and en­ergy bars as you run, ride or swim to keep glyco­gen stores high. Eat­ing enough carbs to thwart a sud­den loss of en­ergy dur­ing an en­durance event is im­prac­ti­cal if not im­pos­si­ble.

The ke­to­genic diet works by re­plac­ing car­bo­hy­drates with fat as the pri­mary fuel source. When you shun carbs and limit pro­tein, your body en­ters a state called ketosis. Even­tu­ally it be­comes “fat adapted” and re­sorts to run­ning on fat in­stead of sug­ars.

That’s ideal for long en­durance events where ac­cess to food is a lim­it­ing fac­tor be­cause once your body is done burn­ing the fat you eat, it starts to burn the fat on your frame. Even if you’re lean, you have enough body fat to fuel nearly any dis­tance race, which is why you won’t lose en­ergy sud­denly.

When a triath­lete lim­its carbs and pro­tein, the body learns to power it­self on fat, not sugar.

“At a very high level, where the small­est edge can mean vic­tory, I’d bet on a ke­to­genic en­durance ath­lete,” says Men’s Health nu­tri­tion ad­vi­sor Mike Rous­sell.

The catch: The diet is de­mand­ing. About 80 per­cent of your calo­ries come from fat, 15 per­cent from pro­tein, and as lit­tle as 5 per­cent from carbs. If you eat 2,500 calo­ries a day, that’s 220g of fat, 90g of pro­tein and 40g of carbs. That’s a lot of eggs, but­ter, av­o­ca­dos and nuts. And you have to eat like this for weeks.

While your body can be­come fully adapted to burn­ing fat as fuel in four weeks, Rous­sell ad­vises en­durance ath­letes to fol­low the diet for eight weeks or longer be­fore com­pet­ing.

Ac­cord­ing to Rous­sell, no cred­i­ble sci­ence op­poses the diet from a health per­spec­tive. How­ever, not ev­ery­one’s bio­chem­istry is suited for ketosis.

When you’re first forc­ing your body into ketosis, you might come down with “keto flu,” with symp­toms that in­clude fa­tigue, brain fog and pos­si­bly ir­ri­tabil­ity. And if you fol­low the diet hap­haz­ardly, you may be­come de­fi­cient in cer­tain nu­tri­ents. Un­less you’re chas­ing epic dis­tance, this may be more trou­ble than it’s worth, and some sci­en­tists are still skep­ti­cal.

“I haven’t yet seen ev­i­dence that the ke­to­genic diet pro­vides a su­pe­rior ap­proach,” says Louise Burke of the Aus­tralian Sports Com­mis­sion.

But some ath­letes swear by it. “I be­lieve a ke­to­genic diet has al­lowed me to train harder,” Bit­ter says. Since he started us­ing the keto diet, he says he hasn’t had that “emo­tional roller coaster” feel­ing where his body feels like it’s shut­ting down on him.

For en­durance ath­letes, that’s the dif­fer­ence be­tween suf­fer­ing from sud­den fa­tigue and en­ergy loss and break­ing the tape.

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