NEW YORK (TheStreet) -- Nobody's perfect -- Warren Buffett included, despite near-constant fawning by fans and observers. The Berkshire Hathaway (BRK.A - Get Report)  (BRK.B - Get Report)  billionaire may be the world's most revered figure in investing, but even he has been known to slip up now and then.

While much of the time, Buffett is right and you should listen to what he says and follow the major principles of his investing strategies, sometimes he isn't and doing what he does could lead to disaster. Here are three pages out of the Oracle of Omaha's playbook you may be better off avoiding. Berkshire Hathaway has not yet responded to request for comment.

1. Don't Invest in Airlines

Buffett got burned on a 1989 purchase of debt in USAir Group, eventually seeing upwards of $350 million go down the drain. He has sworn off airline investing since.

 

"Now if I get the urge to invest in airlines, I call an 800 number, and I say: 'Hello, my name is Warren, and I'm an air-o-holic,'" he has said in the past.

Decades later, the billionaire still considers airline investing to be a death trap.

"Investors have poured their money into airlines and airline manufacturers for 100 years with terrible results" he said at the 2013 Berkshire Hathaway annual shareholders meeting. He has even gone as far as to call his ventures in the sector "temporary insanity."

But airline investing can actually be pretty profitable -- or at least it has been lately.

Airlines had a big year in 2014, and companies like American Airlines (AAL - Get Report) , Delta (DAL - Get Report) , Jet Blue (JBLU - Get Report) and Southwest (LUV - Get Report) watched their stocks experience major climbs.

AAL Chart

They've cooled of a bit in 2015, but many still anticipate gains ahead. Other billionaires are making big bucks on air too, including David Tepper, who has a sizable position in American and Delta, and Ray Dalio, who has a stake in Southwest.

2. Only Invest in the S&P 500

Warren Buffett's advice for most investors is pretty straightforward: Put 10% of your money in short-term government bonds and 90% in a low-cost S&P 500 index fund. He is currently in the midst of a 10-year bet to support this advice. 

But S&P 500 indexes aren't how Buffett has built his fortune. For proof, look no further than Berkshire Hathaway's own documentation.

The firm's most recent annual letter to shareholders highlights that from 1964 to 2014, the per-share market value of Berkshire has posted an overall gain of 1,826,163%. The S&P 500, with dividends included, has risen 11,196%. In other words, Berkshire Hathaway has done 163 times better.

That's not to say S&P 500 investing is a bad idea – in fact, his S&P vs. hedge fund wager is working out heavily in his favor. But you may not want to follow Buffett's suggestions on that front blindly, either.

To quote Warren Buffett himself, "you only have to do a very few things right in your life so long as you don't do too many things wrong." And even on the Oracle of Omaha's advice, you're better off taking a step back to consider what's right for you - and what's wrong.

3. Eat Like a Six-Year-Old

Warren Buffett's eating habits are questionable, at best.

The billionaire explained that he is "one quarter Coca-Cola" in an interview earlier this year. "If I eat 2,700 calories a day, a quarter of that is Coca-Cola (KO - Get Report)," he said. "I drink at least five 12-ounce servings. I do it everyday."

That means Mr. Buffett is ingesting at least 195 grams of sugar daily -- nearly eight times the amount recommended by the World Health Organization.

His reasoning, as he explained it, is that eating like a first grader is his best bet for not dying. "I checked the actuarial tables, and the lowest death rate is among six-year-olds. So I decided to eat like a six-year-old. It's the safest course I can take," he said.

His diet strategy also entails Utz Potato Stix and chocolate chip ice cream for breakfast. You may want to consult with your doctor before doing the same.

There is ample scientific research recommending against diets that are high in fat and sugar. There are even studies that suggest it inhibits learning. The Oracle of Omaha is a brilliant investor, but his diet may not be helping him make smarter decisions.

This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.

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