Slimming down after having my son last May took some work, but I had the season on my side. Summer's glorious bounty of vegetables made losing weight seem relatively simple: I'd pick whatever veggies looked fresh at the market and then throw them on the grill with a lean source of protein, such as chicken or fish. Then, I'd round out the meal with a reasonable portion of a healthy carb-based side, such as brown rice. But as fall creeps on and winter draws near, I've realized that my secret weight-loss weapon-in-season vegetables-works all year round. Incorporating these five fresh-right-now vegetables into your diet plan can help you win the weight-loss battle this winter.

Potatoes: They've gotten a bad rap for scoring high on the glycemic index-which reflects how much blood glucose rises after eating a food-but a new study out of the University of California, Davis (funded by the Potato Board) suggests that eating even a potato a day doesn't sabotage weight loss so long as one is following a healthy calorie-controlled regimen. One medium potato (5.3 ounces) has a surprisingly reasonable 110 calories.

Related Recipes: 21 Skinny Potato Recipes

Cauliflower: At only 29 calories per cup, cauliflower is a low-calorie side-but, prepared well, it feels substantial. Blend it into a creamy puree, roast it to draw out its nutty flavor, eat it raw in a chopped salad. This veggie's mild flavor makes it very versatile.

Kale: This vegetable is pretty much synonymous with good health-and for good reason: it's a great source of beta carotene, vitamin C and phytochemicals, called isothiocyanates, that amp up the body's detoxifying enzymes. Kale is also a great vegetable to have on hand when you're trying to cut calories. Why? Kale is awesome in soups and, according to several research studies, soups tend to be über-satisfying, which means you can feel full on fewer calories. (Woo hoo!)

Spaghetti Squash: Kids love spaghetti squash for its "magical" properties: bake it, flake it and this seemingly typical vegetable transforms into "noodles." You'll learn to love it, too, once you realize it can save oodles of calories. Serve spaghetti squash with marinara sauce and a sprinkle of Parmesan in place of regular spaghetti for a dish that delivers less than a quarter of the calories. (Cooked pasta has about 200 calories per cup; spaghetti squash, 42 calories.)

Brussels Sprouts: Low in calories and a respectable source of fiber (28 calories and 2 grams per half cup), these tender, sweet vegetables are a great side to serve every night-as well as an elegant dish to share at Thanksgiving. Like kale, they're a source of isothiocyanates. They also deliver vitamins A, C and K.