What is the difference between calories and calories from fat? Why are they different numbers? Which should I follow to maintain and/or lose weight?
On food labels, the “calories” stands for the total calories in one serving from all sources—fat, carbohydrates, and protein. The “calories from fat” stands for just the calories you’re receiving from fat.
When it comes to weight loss, conventional wisdom suggests that you should consume fewer calories than you expend each day. So if you take in 2,000 calories per day you can maintain your weight by expending 2,000 calories, and lose weight if you expend more than 2,000 calories. More recent evidence suggests that not all calories are the same, however. The idea of “good calories” and “bad calories” seems to indicate that calories from fats and carbohydrates may affect the body in ways that can impact weight gain and weight loss. If you haven't read it yet, I'd recommend that you read some of the articles on carbs, fats, and calories on the diabetes page. It may help clear up some of the confusion.
That being said, fat intake is important to monitor. It affects your overall health and heart disease risk. Total fat intake should be 30% of your total daily calories. So, if you consume 2000 calories each day, no more than 600 calories should come from fat. That is where the "calories from fat" on food labels can come in handy.
Here are a few other articles you may find interesting:
Can’t We Just Swap Out Bad Fats for Good Eats?
You Do Need Fat in Your Diet – Here’s Why