Recently, Bieber fever officially gave way to Bieber fury. But this time, the catalyst wasn’t his crazy fan base–it was his vegan diet. According to RadarOnline.com, Justin Bieber tried to go vegan to placate his mentor Usher, who promised the teen heartthrob that a diet refresh would boost his energy while on tour. (Good man! There are plenty of benefits to eating less meat.) But as an anonymous insider told Star, Beiber’s girlfriend Selena Gomez says that excluding meat, fish, eggs, and other animal products instead turned her boyfriend into a jerk.

Since then, Bieber clearly gave up his vegan diet—when he threw up on stage during a concert last week, he blamed it on drinking too much milk (decidedly not a vegan staple). But his recent forays into going sans meat (and eggs, cheese, dairy and animal products) still left us wondering: Does being a meat martyr really turn you into a meany?

“It’s personal,” says Keri Glassman, registered dietician and Women’s Health nutrition expert. “Some people feel better without meat in their diets, while some people feel worse.” One possible explanation: Newbie vegetarians or vegans may just be hungry. Because protein and fat from meat have more calories per gram than the carbohydrates in an all-veggie diet, a vegan diet may leave you feeling empty physically—and emotionally. “You’re going to feel unsatisfied and constantly hungry if you’re not eating enough calories because you’re not eating meat, or because you’re eating an unbalanced diet,” Glassman says. “And when you don’t have enough calories, you don’t have enough fuel, and you become irritable and cranky and lethargic.”

The good news is that it’s possible to change your diet in a way that won’t drive you (or your friends) completely bonkers.

How to Stay Sane on a New Diet

1. Eat breakfast every day. Begin the day with a breakfast that includes whole grains, protein, colorful fruits and vegetables, and you’ll reap the benefits of a better mood–not to mention clarity of thought, better performance at school or work, fewer food cravings, and an all-around easier time managing your weight, says Elizabeth Somer, registered dietician and author of Eat Your Way to Happiness.

2. Chow down at regular intervals. Eat regularly to steady your blood sugar level: it’ll keep you from becoming irrationally irritable when the waiter forgets to serve your dressing on the side (what part of ON THE SIDE was not clear?) or when a fellow driver cuts you off (that %!^@# !!!). (Read more about the best time to eat.)

3. Follow the 75 percent rule. Make sure that at least 75 percent of each meal and snack you eat consists of real, unprocessed foods. A 2009 study of nearly 3500 adults published in The British Journal of Psychiatry found a link between high consumption of processed foods (desserts, fried food, processed meats—the works) and the likelihood of depression. But here’s a reason to put a smile on your face: a diet rich in whole foods provides you with the most nutritional bang for your caloric buck—you get all the nutrients and none of the useless filler, whereas with processed foods you’re only getting a fraction of the nutrients per calorie.

4. Pee pale. Drink enough water so that your urine is pale yellow, and you’ll stave off dehydration. The first sign of dehydration is fatigue, a slippery slope toward unleashing your bitchy alter ego. (Worse yet? Dehydration makes you suck at everything.)

5. Swallow this: A moderate dose multivitamin, plus extra calcium, magnesium, vitamin D, and—especially for non salmon-eaters—a DHA supplement of at least 220 mg will help fill in any gaps in your new diet and steady your mood, says Somer. Vitamin D, in particular, feeds receptors in your brain that need vitamin D to keep hunger and cravings in check, as well as to pump up levels of the mood-boosting chemical serotonin.

More from WH:
6 Reasons to Eat Less Meat
Vegetarian Eating FAQs
The Real Scoop on the Raw Food Diet

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