Using on sale, for sale, buy etc are good keyword modifiers because people who want to purchase will use these terms to filter sites that don't sell the product. I try to include these in the meta description and if it is a product "on sale" or it is a sale price I'd likely include it in the Title as a call to action. The bottom line is fat burner is still your primary keyword and the modifiers quite often are not very competitive terms so they are much easier to place at the top.

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