Dieters often try to eat low-calorie foods to lose weight. You might buy foods labeled “low-fat,” “reduced calorie,” or “lite” at the grocery store to help with your weight loss plan. You might also try to cook with low-calorie foods at home. But sometimes, low-calorie foods for weight loss are bad for your diet.

What Are “Low Calorie” Foods?

You’ll see many packaged foods at the grocery store that are labeled as “lite,” “light,” “low-calorie,” or “low-fat.”  These foods are especially attractive to dieters who are trying to cut calories.

Even more appealing are foods labeled “fat-free,” or “low-fat.”
But if you don’t know what those labels mean, your diet may be headed for trouble.  The Food and Drug Administration (FDA) and the United States Department of Agriculture (USDA) have specific labeling guidelines for food that govern the use of these promotional terms. The guidelines are designed to help consumers make better food choices. But they can also be used by food manufacturers to make foods look more appealing than they really are.“low-fat,” 

For example, a food that is labeled “fat-free” does not have to be free from fat.  According to FDA guidelines, it must provide less than .5 grams per serving of fat. So a product like certain brands of coffee creamer might contain .4 grams of fat per serving and still be labeled “fat-free” in compliance with the rules.

So why does that tiny amount of fat matter? Because you may consume more than a single serving when you enjoy that food.

Again, coffee creamer is a good example. Many dieters will pour two, three, or even four times the serving size into their cup in the morning.  As the servings add up, so do the fat grams and calories.
“Low-calorie” or “Light” are confusing terms as well. According to USDA guidelines, these foods must contain 25% fewer calories (“reduced calorie”) or 50% fewer calories (“low-calorie”) than a comparable reference food.

But if that reference food is high in calories, then the reduced calorie food might also be high in calories, and still not good for your diet.

Should You Buy Low Fat or Light Foods?

Some studies have shown that we tend to overeat foods that carry certain food labels like “healthy,” “light” or “low-fat.”  If you consider that these foods might not be low in calories or free from fat, choosing light foods may cause you to consume more calories overall.
Also, some food manufactures reduce fat or calories by adding ingredients that may not be good for your diet. For example, many fat-free salad dressings are made with sugar and some fat-free coffee creamers are made with high fructose corn syrup.

So should you avoid fat-free or low-calorie foods altogether? You certainly don’t have to. But there are three smart rules you can follow to keep your diet on track.

Read labels carefully. Make sure you evaluate the serving size of each food you buy and think about the number of servings you are likely to consume. Then decide if the low-calorie or low-fat food is the best choice for you.
Check the ingredients list. Ignore the advertising on the front of the food package label. Instead, check the Ingredients List to see if your food is healthy. See if hydrogenated oils, high fructose corn syrup or other sweeteners have been added to your food to provide texture or flavor.

Find foods that are naturally low in fat and calories. Some foods are low in calories and low in fat without any processing at all. These foods are likely to be good for your diet. Fresh fruits and vegetables and lean meats provide plenty of nutrients without too much fat or too many calories. These are the foods that will fuel your body and keep your diet on track.
https://www.verywell.com/portion-size-mistakes-you-can-avoid-3495774