I’ve spent the past couple of months learning more about pet obesity than you thought you’d ever want to know. It’s part of a new drive to help my clients get a grip on the fat that threatens to consume their pets’ health and well being.

But since the advent of Pfizer's Slentrol, my investigation has taken a new slant. What’s the deal with this dog-slimming diet drug? “Obesity begone!” it claims. But does it hold up to the reality of its promise?

The answer? Yes. It works. It will strip pounds off your dog in two ways: First, by reducing your dog’s appetite drive. Second, by reducing fat absorption in the GI tract. The laboratory results are conclusive and FDA-worthy. 

You might think an obesity drug is a brilliant no-brainer and you’re anxious to give it a whirl. Or perhaps you’re like me and you’re skeptical of any drug—especially one that’s been eluding human researchers for decades. After all, billions of dollars go into human drug research every year for a malady that’s reaching pandemic levels all over the world. So how is it that dogs get a safe and effective drug for obesity before humans do?

According to a UC Davis researcher (I don’t name her because I haven’t secured her permission yet), the drug does its thing. But it doesn’t do it once it’s no longer administered. Her take? The drug works in highly controlled settings—but it’s not practical in real life situations.

In fact, dogs exhibit the rebound effect most yo-yo dieters know so well. Once the drug is withdrawn, dogs end up gaining back the weight—even when their caloric intake doesn’t increase back to its normal levels. And that’s because it seems the caloric requirement for a dog is re-set to a new, lower level after using Slentrol. Take away the low fat absorption the drug enables and next thing you know, she’s back to her pre-Slentrol weight—or beyond.

Caution, here: This is a new drug and I’m reporting raw, unpublished, possibly still-anectdotal findings. But it jibes well with what we know about the drawbacks of human obesity drugs. And it’s not so hard to believe that dogs are no different than humans when it comes to basic metabolism and weight control issues, is it?

The upshot? There’s probably no magic pill, folks. But that doesn’t mean Slentrol has no medical value. There will always be some situations where rapid weight loss is crucial to survival. For example, when I ran this past a vet surgeon the other day, he mentioned that the drug might become a viable tool for dogs who need emergency weight loss before and after orthopedic surgery.

But long-term weight loss? Not likely. But the jury's still out. So it’s back to what we know really works for people: increased exercise and decreased calories. It’s a tough break for all of us hoping for the best from a pill—but reality isn’t always as rosy as we’d like it to be.