A five-mile run is good for a double-dip cone of Rocky Road. A 45-minute workout with Jane Fonda's videotape equals a slice of plain pizza, a 90-minute dance class will burn up five oatmeal-raisin cookies and one hour's writing on a computer terminal is worth a boiled potato.

These are some of the hard truths I discovered after wearing a personal microcomputer, called a Cal Count, for one week. The two-ounce, battery-powered device, although resembling an innocent paging "beeper," reveals in brutally honest digital display the number of calories your body is burning minute-by-minute during any activity.

Created by biomedical engineer Elmer Lipsey in 1978 for patients recovering from heart attacks, the device was modified for and marketed to the fitness-fixated public in 1980. So far, the 60-year-old McLean, Va., inventor has sold about 20,000 units--at $89 each--and says sales are "steadily increasing."

"People can figure out how many calories they take in by using a calorie counter," he says, "but until now they've never been able to tell exactly how many calories they're using up."

Caloric usage tables "can only give an approximate figure," he claims, since each person moves and metabolizes calories uniquely. Also, "there's never before been a device to measure activity that didn't interfere with the activity itself."

To program the tiny computer, a user enters personal data--age, gender, height and weight--which allows the gadget to calculate basic metabolic rate. When the Cal Count is clipped onto a belt or slipped into an inside pocket, a motion sensor within the machine determines intensity of the activity being performed--from zero for sitting still to nine for peak activity--and displays a running total of calories burned.

"People either swear by the machine," says the 6-foot, 207-pound Lipsey, "or swear at it. Most people don't realize how few calories they actually burn."

As a 29-year-old, 112-pound, 5-foot-4 female, I burned the following calories--according to my Cal Count--during a half-hour of these activities:

* Running (9-minute mile), 309

* Bicycling, 150

* Jane Fonda's Workout, 120

* Dance class, 105

* Mini-trampoline, vigorous jumping, 274

* Walking, 125

* Writing on a computer terminal, 38

* Housework, 76

* Sleeping, 28

The 24-hour total: 1,600 on a low-activity day, 2,400 on a high-activity day.

In contrast, a 46-year-old male colleague (160 pounds, 5-foot-7) burned 96 calories during 20 minutes of calisthenics and 365 calories in a half-hour of running (8-minute mile).

For those loathe to shell out 90 bucks to learn this difficult-to-digest information, Lipsey offers these caloric-consumption rules of thumb:

"You burn about 100 calories per 100 pounds of body weight per mile . . . One pound equals 3,500 calories. So if you eat 500 calories roughly one quarter-pound cheeseburger more than you use per day, in a week you'll gain a pound."

Some activities are particularly hard to gauge, however, even with a Cal Count. I had a tough time calculating a "hanging workout" in gravity-inversion boots, for example, since the microcomputer must be kept right-side-up.

Also, Lipsey notes, "People always ask me where to wear it during sex. I say 'be creative.' Some people have jokingly told me they burn five calories, others have said they burn 280."

* Running Wild: Obsessive running by males may be that gender's counterpart to the self-starvation emotional disorder anorexia nervosa, commonly confined to females, according to "preliminary observations" reported in the Feb. 3 New England Journal of Medicine.

After interviewing about 60 men who run more than 50 miles a week, three University of Arizona researchers defined a subgroup of "obligatory runners" who view running as "a consuming goal that preempts all other interests in life."

These male runners "resemble anorexic women in terms of family background, socio-economic class and such personality characteristics as inhibition of anger, extraordinarily high self-expectations, tolerance of physical discomfort, denial of potentially serious debility and a tendency toward depression," report psychiatrists Alayne Yates and Kevin Leehey and psychologist Catherine Shisslak--all three runners.

While the anorexic's goal is "physical attractiveness," they note, the obligatory runner's goal is "physical effectiveness . . . The gender variance may be accounted for by the fact that our culture values women for their beauty and men for their athletic prowess."

Aside from gender, the major difference between anorexics and obligatory runners is that "anorexia commences in adolescence, whereas most of our obligatory runners became unequivocally committed to running in the third to fifth decade of their lives." Both behaviors, they speculate, may be attempts to establish an identity.

"The girl's physical attractiveness is commonly put to the test as she enters the dating arena," says the report, while the male's identity crisis often "occurs in adulthood when careers stabilize and physical or sexual prowess begins to decline noticeably."

* All That Jazzercise: Enthusiasts of aerobic-style dance know that boogie is good for their heart. And dancers in this Saturday's "Danny Dance for Heart" kickoff at George Washington University's Smith Center also will benefit the hearts of others. Proceeds from the $5 half-hour demonstration and 90-minute Jazzercise class will go to area American Heart Associations.

Registration is 9:30 to 10 a.m., entertainment starts at 10 and the class runs from 10:30 to noon. The event, sponsored by Danny frozen yogurt, kicks off a month of AHA dance benefits. For more information: 337-6400.

* Eye Love View: Increasing numbers of racquetball players are keeping their eye on the ball--literally, reports Toronto ophthalmologist Michael Easterbrook in National Racquetball magazine. The incidence of eye injuries on the racquetball court is increasing each year, he says, often to players wearing eye guards who are "lured into a false sense of security."

After testing eye guards as chairman of the Canadian Standards Association (CSA) committee on eye protection in racket sports, Easterbrook concludes, "Any open eye guard on the market can be penetrated by a racquetball traveling at only 50 miles per hour, and the average beginning player hits the ball over 70 mph."

He recommends wearing eye guards made with polycarbonate--an impact-resistant material that will not break at speeds of up to 100 mph.

New standards for eye guards, says Easterbrook, should eliminate 99 percent of the nearly 70,000 racket-sport-related eye injuries in in the United States annually. The proposed standards are expected to be approved soon by CSA and the American Society for Testing and Materials. Open eye guards will not pass. graphics/photo: Cal Count