An acquaintance sent me an article the other day: Student from Cornell University Loses 37lbs in 1 Month With No Diet or Exercise!
The “article” is really an ad for a supplement that is “all natural” and has magical properties of preventing your body from functioning properly, causing severe weight loss in a short period of time.
Unless you’ve had gastric bypass surgery, you should not lose anything close to 40 pounds in a month. (Even some people with gastric bypass don’t lose that much that fast!)
One or two pounds a week at most.
If you cut all the junk (wheat, dairy, sugar, alcohol, etc.), you’re going to lose a lot of water weight fairly quickly. (In addition to helping pack on fat, those foods promote water retention. So the Current Fad Diet will give you larger losses in the first week or two, because of the water.
Anything that is promising you more than a pound or two per week (that’s 10 or less per month) is snake oil.
(And any diet that promises all that isn’t sustainable long-term.)