Until a few days ago when a correspondent asked me about two recent books dealing with leptin, I had assumed that interest in this hormone that can cause obesity had waned. There was a big flurry of interest in the early 1990s, when the first leptin studies came out, but little in the popular press since then.

But the scientific study of leptin and its role in causing obesity has continued. A search of PubMed for the scientific studies that MEDLINE indexes returns more than 10,000 hits. Of these, 1,500 deal with both leptin and diabetes.

There seems to be no question that too much circulating leptin leads to obesity. It may even lead to type 2 diabetes, since obesity and type 2 diabetes have some relationship, which however no one seems to understand exactly. At least the scientists are hardly in agreement on that relationship.

The study of leptin seems to be frustrating, and the books about it reflect that frustration. We don’t have any leptin drug to help us lose weight, which one of the books about leptin implies is the reason that popular interest in leptin has waned.

That book, Mastering Leptin by Byron J. Richards, is in fact one of the most frustrating and incomprehensible books that I have ever read. It takes forever to get to the point, and when it does, it seems to me to be an incomprehensible jumble of claims that mastering leptin will cure almost every know malady.

Mastering leptin may be important. But the claims in the book of that name strike me as just too good to be true.

The other book based on leptin is The Rosedale Diet by Dr. Ron Rosedale. This one is a lot easier going. But it doesn’t really make the case that the Rosedale diet has anything to do with leptin.

Still, the leptin connection doesn’t really matter. This is an outstandingly good diet. I agree with almost everything, except:

1. Dr. Rosedale prohibits carrots for no good reason. It is based on old, discredited research. Five years ago I wrote about the new carrot research in my “Diabetes Update” newsletter.

2. He doesn’t say why he bans most beans, which are almost all quite low glycemic and high protein.

3. He makes a fundamental mistake in understanding the glycemic index when he writes that it measures only glucose and not the other sugars. While glucose is the index of 100, the glycemic index measures the total effect of a food on blood glucose. He seems to be confusing the glucose in our food with the glucose in our blood.

4. He recommends just 15 minutes of daily exercise. Most everyone else will tell you that is not enough. But it certainly is better than most people are getting.

Mastering Leptin is also a diet book, subtitled The Leptin Diet. Strangely, this diet and the Rosedale diet seem to have little in common.

The one common link that I identified is eating low carbohydrate. The Richards diet has “five rules,” one of which is “to reduce the amount of carbohydrates eaten.” The Rosedale diet would also have us cut back on our carbs, but with more specifics.