Dressings can be the downfall of many otherwise-healthy salads. Lots of salad dressings pack more than 120 calories and 12 fat grams into just two tablespoons — and many people use twice that amount.

So when Jan Margrave asked me to lighten up the dressing she loves, I rolled up my sleeves and took the challenge.

"My favorite salad dressing in the world is Thousand Island," she wrote. She prefers the Litehouse brand, which has 130 calories and 13 grams of fat in each 2-tablespoon serving. "Any chance you could get me a recipe for a lighter Thousand Island dressing, but one that doesn't taste bland? Mine has so many calories."

I found a bunch of Thousand Island recipes, and most of them didn't agree on the ingredients. Some called for hard-boiled eggs while others required dill pickles, pimientos, capers or sweet pickle relish.

I decided to experiment with a version that includes chili sauce and horseradish because there's nothing bland about that. Prepared horseradish — not to be confused with horseradish sauce — adds a lot of flavor to this dressing for less than 1 calorie.

Now that's my kind of ingredient.

And using light mayonnaise instead of regular trims 800 calories and 96 fat grams from this recipe.

The slimmed-down dressing tasted so good that it inspired me to take another step and make over a Reuben sandwich.

A typical Reuben sandwich includes Thousand Island dressing, corned beef, Swiss cheese, sauerkraut and rye bread. Most recipes say to fry the sandwich in butter, as if the sandwich wasn't high enough in fat and calories.

A medium Angus corned beef Reuben contains 918 calories and 41 fat grams. If you ate two Quarter Pounders from McDonald's instead, you'd save 98 calories and 3 grams of fat. Wow.

I put this sandwich on a diet by using thinly sliced corned beef — and less of it. Choosing Swiss cheese made with 2 percent milk and topping the sandwich with the lighter Thousand Island dressing trims more fat and calories. I found a rye bread that has more fiber than many other brands, and instead of frying the sandwich in tablespoons of butter, I just put a little cooking spray on my griddle.

The result: You save 503 calories and 29 fat grams. My sandwich slices the calorie count by 55 percent and the fat by 70 percent.

Compared to Litehouse, this Thousand Island dressing — 75 calories and 3.3 fat grams per 2-tablespoon serving — cuts the calories by 42 percent and trims the fat by 75 percent.

Want more healthy salad dressings? I have a bunch, and I'll be sharing my recipes for three of them — blue cheese, French and ranch — next week.

KATHY'S THOUSAND ISLAND DRESSING