Fit Facts and Figures

by Jerry Brainum


Pregnant women pro­duce larger amounts of en­dorphins, body chemicals that reduce pain. Exercise also raises endorphin levels. So what happens if pregnant women exercise throughout their pregnan­ies?

Researchers in Italy had 18 pregnant women exer­cise on stationary bikes throughout their term. Another 18 pregnant women didn't exercise. Those who exercised had higher endorphin levels and felt far less pain during labor. (Am J Ob-Gyn 160; 3:707-12, 1989)

Medicine 82 percent of the 500 doctors polled de­clared that they regularly prescribe exercise to depressed or anxious patients.

We know that some­thing about exercise makes people feel good, but the question is, exactly what is the mechanism involved? Several theories account for the uplifting mental ef­fect associated with vigorous exercise. The most popular involves a brain chemical called beta-endorphin, which is pro­duced in the brain under times of perceived stress, including the stress of ex­ercise. Beta-endorphin is quite potent in its pain-kil­ling effects, estimated to be I00 to 1,000 times more potent than morphine; but beta-endorphin does more than just relieve pain—it also induces a feeling of well-being.

The levels of beta-en­dorphin increase fivefold after just 12 minutes of vigorous exercise and re­main elevated for 30 minutes after exercise.



Some people ascribe the recently recognized syn­drome of "exerciser's ad­diction" to beta-endorphin, noting that when people af­flicted with this condition don't exercise, they show symptoms similar to those seen during withdrawal from drugs.

Not everyone, however, agrees with the beta-endor­phin theory. The skeptics say that there's no proof that high levels of beta-en­dorphin pass through the protective blood-brain bar­rier. In addition, when naltrexone, a substance that blocks the effects of beta-endorphin, is given to exercisers, they still ex­perience the "good feel­ings" from exercise.

Another theory states that exercise produces a mental boost through in­creased secretion of other brain chemicals called catecholamines, particu­larly norepinephrine. This makes sense because men­tal depression often stems from a deficiency of this chemical. In fact, most an­tidepressant drugs work by



The motivation to exer­cise varies among different people. Some people exer­cise to lose weight, others to gain weight. Others are satisfied with their weight but want to add muscle tone or shape. Still another group exercises for reha­bilitative reasons—for ex­ample, heart patients or people with arthritis. Then, of course, there are body­builders, most of whom ex­ ercise for competitive purposes—that is, body­building competition. Whatever the motivation, however, all these people share one thing in com­mon: Exercise makes them feel good.

The effects of exercise appear to be psychoso­matic, or involving an in­teraction between the brain and body. This fact is well-known to physicians. In a 1987 survey appearing in the Physician and Sports


increasing the brain's supply of norepinephrine.

Exercise increases
norepinephrine levels 10 times over base level; how­ever, the level returns to normal 10 minutes after exercise ceases. Regular exercisers produce more of this stress-fighting sub­stance, which supposedly makes them feel happier and less stressed.

The elevated body heat associated with exercise, by relaxing your muscles, may be another reason for the good feelings of exer­cise. Core body tempera­ture can elevate to as high as 104 degrees during exer­cise and remain high for several hours after exercise ends. Some physiologists have found that exercise can have relaxing effects similar to that of sauna baths. The mechanism is relief of muscular tension through heat.

This relaxation effect is especially useful for people suffering from mental anxiety. Many drugs such as Valium work by relieving muscle ten­sion; without muscle ten­sion anxiety cannot be expressed. In other words, you can't be tensed and re­laxed simultaneously. Stu­dies show that exercise, by relieving built-up muscular tension, is as effective as drugs—without the side ef­fects of drugs.

Repetitive exercise, such as running, cycling or swimming, tends to shut down the reasoning, logi­cal side of the brain (the left hemisphere) and stimulate the creative, more abstract right half of the brain. In this way exercise stimu­lates both creativity and clearer thinking. The com­bination of a relaxed body free from tension and a clearer thinking brain al­lows you to deal more con­structively with perplexing


Finally, exercise pro­duces a built-in motivating effect. As you see yourself improve—whether this means less flab and more muscle or just better shape—you'll improve


For some years research has linked a high intake of dietary fat with increased risk for developing various types of cancer. One recent study shows a possible rea­son for this effect.

Ingesting large amounts of polyunsaturated fats, such as vegetable oils, in­hibits the ability of immune factors called T- cells from ' destroying cancers. These fats also speed up tumor formation.

One cell in particular that's inhibited by a high-fat intake is the natural

both your confidence and outlook on life. The old adage that says you have to love yourself before you can love anyone else is readily apparent here. And love makes everyone feel good.

killer cell. These constitute the body's first line of defense against cancer. A high-fat intake increases production of the 2-series prostaglandins made from the fatty acid arachidonic acid, and it's these prosta­glandins that directly in­hibit immune function.

When you follow a low-fat diet, your body synthe­sizes less prostaglandin and the immune system functions more effectively to destroy cancer before it spreads. This is one of the reasons eating a lowfat diet helps to prevent cancer. (Am J Clin Nutt- 50:861- 867 , 1989)