In an earlier post, I talked about how juice drinks, smoothies, and shakes all have a place in a healthy diet—especially if you’re trying to slim down. I’m a big fan of all three myself, especially on busy days when there’s no time to cook. But here’s the deal: There’s a right way and a wrong way to add these slimming drinks to your diet. Do it the wrong way, and your meals-in-a-glass might be doing you more harm than good. So when you reach for that juicer or blender, make sure you avoid these five common smoothie mistakes.

1. Overdoing the fruit or starchy veggies.

I mentioned this in my earlier post, but I’m repeating it because this is one of the biggest diet mistakes people make. It’s true that fruits and starchy vegetables are good for you—but overdoing these foods will put pounds on you, rather than taking them off.

If you’re trying to lose weight, your best bet is to stick to one serving of fruit per drink. This translates into half an individual piece (for instance, half an apple or half a banana) or half a cup of berries, grapes, or tropical fruits—about a closed fistful. Similarly, limit starchy veggies like beets and carrots to one baseball-sized serving at most.

2. Sticking to the same old, same old.

It’s great to have favorite recipes, but I’m a believer in varying your ingredients because it’s the best way to guarantee that you get a full range of nutrients without overloading your body with any one food.

Remember that there are thousands of phytonutrients, and the more of them you feed your body, the better. And while it’s unlikely that you’ll get too high a dose of potentially problematic plant ingredients like alkaloids, oxalates, and goitrogens even if you use the same veggies each day, why take a chance?

Instead, rotate your greens—kale, spinach, chard, Romaine, and arugula are fun choices—and change up your fruits on a regular basis. Also, buy fresh produce that’s in season whenever you can.

3. Skipping the fat.

Fat satisfies your cravings, keeps your skin smooth, and helps you burn fat more quickly. So no matter which drink you choose, toss in a little avocado, some coconut oil, or some nuts to “fatten it up.”

4. Getting too little protein.

You might think that skipping protein-rich shakes and opting for drinks that only contain fruits and veggies will help you take weight off faster. However, if you’re replacing lots of your meals with drinks, I strongly recommend choosing shakes a good part of the time. You need that protein to heal and repair your body, optimize your metabolism, and keep cravings from sabotaging your diet.

5. Using an inferior protein powder.

To be blunt, there’s a lot of junk out there. Grocery and health-food stores are loaded with protein powders made from low-quality ingredients like soy, whey, or factory-farmed animals. Quality matters when it comes to your health, so don’t simply reach for the cheapest protein powder you can buy. Instead, look for high-quality products made from pastured beef, like my Bone Broth Protein and my Orange Cream Collagen Cooler. In addition to being better for you, a high-quality protein powder tastes a whole lot better.

— If you follow these simple rules, your shakes, smoothies, and juice drinks will do just what you want them to do: slim you down, detoxify your body, and give you glowing skin. So get out your juicer or blender, give your healthy ingredients a whirl, and raise a glass to a younger, healthier you in the New Year.

Cheers!