So simple, so effective!

Combining intermittent fasting with a clean food formula is a surefire way to boost metabolism and power off the pounds. And according to

Ian K. Smith, M.D., who outlines his plan in Clean & Lean, it only takes 30 days! “Intermittent fasting is a proven weight-loss tool, and clean eating also promotes weight loss,” he says. “It turns out, the benefits are synergistic—and it’s easy enough that anyone can follow the plan long enough to get results.”

Throughout the 30-day plan, you’ll enjoy three meals and three snacks each day. “It’s important to distribute your calories throughout the eating window so your energy doesn’t fade,” he explains. That said, if you’re not hungry, it’s okay to skip a snack here or there—just make sure you have a healthy nosh (like an apple with almond butter or a hard-boiled egg) at the ready in case hunger strikes.

At mealtimes, you’ll fill your plate with Dr. Smith’s 30 Clean & Lean Foods (see list below). Don’t see your favorite food? Dr. Smith says the list is flexible, but the key is to focus on natural, minimally processed foods and avoid harmful additives and synthetic chemicals that can sabotage your weight-loss efforts.

You’ll aim to eat all of your meals and snacks between 9 am and 7 pm, but you can shift those hours to fit your needs and lifestyle, says Dr. Smith. “Just remember, the smaller the window, the better chance you have of getting good results.”

Throughout your fasting period, Dr. Smith recommends drinking plenty of water and herbal tea as well as black coffee. And for your speediest slimdown, incorporate these simple success strategies:

Keep your eating window early. “This sets you up to burn more fat and feel less hungry for the rest of the day,” Dr. Smith explains. In fact, researchers at the Pennington Biomedical Research Center in Baton Rouge, Louisiana, report that dieters who ate their last meal earlier in the day had significantly lower levels of fat-storage hormones than those who started fasting closer to bedtime. The reason: If the body is still digesting when it’s time for bed, it can’t easily switch into detox mode, slowing weight loss. But you don’t have to be an early riser to get the benefits: Even eating a larger lunch and a lighter dinner has been shown to speed weight loss.

Go for crunchy snacks. “This is a great way to suppress your appetite,” asserts Dr. Smith. Indeed, gastrophysicists at the University of Oxford in England report that the brain correlates crunchiness with abundant nutrients, triggering the release of satiety hormones, while a study in the journal Food Quality and Preference showed that enjoying a crunchy snack can reduce subsequent hunger by 43%. To get the benefits, choose “noisy” snacks like carrots, celery, apples or nuts.

Keep your glass full. Dr. Smith recommends consuming at least eight 8-oz. glasses of water or unsweetened tea each day. Not only does liquid fill you up, he says, it also plays a vital role in ferrying toxins out of the body. He suggests jazzing things up by soaking

lemon slices, watermelon chunks or mint leaves in your water.

Recruit a friend. Having a “diet buddy” makes it easier to succeed, says Dr. Smith. “Life transformations are not easy. Having someone who is going to lift you up when you want to quit and keep you accountable—that can make a big difference.” In a study at the University of Pittsburgh School of Medicine, dieters who recruited three friends to assist in their weightloss efforts were 20% more likely to succeed and 40% more likely to keep the weight off than those with no support system. No buddy? No problem! Download the “hiitide” app on your cellphone and sign up for “Dr. Ian’s World” for access to message boards, a dedicated expert coach and opportunities to connect with Dr. Smith.