The gimmicks to help people diet are legion: operations to bypass the intestines or to wire jaws shut; the grapefruit diet; the Mayo clinic diet. There are high-fat, low-carbohydrate, high-protein diets. Fasting. Drinking. Eating all you want. And, of course, the latest fad - liquid protein.

Actually, it is not the latest. There are two much newer developments in dieting equipment: One is a computer; the other a fork.

Not just an ordinary fork, but a fork guaranteed to make it impossible to pick up any food. Advertised as "a new twist in weight control," the silverplated, $6.95 number is available with directions on its other uses: It can be bent into a napkin or scarf ring; or shaped to wear as a choker. The tines can be turned up to make it a wall hook. In other words, it can be used for many things except eating.

It is, according to the brochure that accompanies it, ". . . designed to not pick up food. We could have offered you a handle," the copy goes on to say, "but that would be silly."

Woodward and Lathrop is selling the diet fork.

If you want to spend a great deal more, you can purchase a mini-computer, part of the Countdown Permanent Weight Loss System.THe complete package also contains a guidebook, two nine-week bite charts, a progress chart, a grease pencil and the battery to operate the computer. It costs $24.95 and is described by its manufacturer, Teledyne Water Pik, as "an electronic learning device that monitors the amount of food you consume and the speed of your food intake. Before each bite is taken, the user presses the counter/pacer (computer) which flashes a light at regular intervals." According to the directions the user must chew at the same rate as the light blinks.

The concept behind the computer is actually quite sound. It tries to deal with how you eat rather than what you eat. Behavior modification to slow down your eating. The theory is if you slow down eventually you will eat less.

Whether you are likely to do so with a book as a guide and a computer with a blinking red light is something else. But people who are willing to spend $10 or $15 a week for liquid protein probably won't think twice about $25 for a computer.