Weight Is a Funny Thing (Sometimes)

I don't get weight. Are scales made to intentionally throw people off? Is it a guesstimation? Is there a certain scale that is like Greenwich, England when it comes to time?

I'll eat healthy one day, work out, feel trimmer, and lose a few pounds. So, I'll instantly be thinking, "Hey, this works." But, the next day, I'll eat just as healthy, work out just as much, and then what happens? I gain the weight back. On some days when I don't eat as healthy and perhaps take a day off from working out, I'll lose pounds and then the next day when I eat healthy and work out, I put those pounds back on. What's the deal there? Is there a certain pattern I can get into where I can get trimmer on the days I work out and eat healthy as well as the days I don't do either? If that's the case, then I can't seem to figure out the pattern.

If anyone has any tips, please feel free to let me know, because, I'm stumped.