By Subscribing, you'll receive advance notice of new products, reviews by our instructors, gear and travel specials and more.
By Fred Bove, M.D., Ph.D.
I was running along a favorite trail recently, when I came upon a longtime friend. We ran together to catch up on events and, during our conversation, the subject fell to nutrition. He was trying to sort out a large amount of information he had researched about diets. These are usually described for specific goals (body building, lowering cholesterol and weight loss), often by advocates of a specific diet method, with little information upon which to base an informed decision about what and how much to eat. In trying to learn about healthy eating, my friend had become increasingly confused.
I note similar confusion among my patients when they ask about a new diet, vitamin or food supplement that is being discussed in the press. I try to provide them with nutritional guidelines that can be used on a long term basis, not for a short term specific goal, such as rapid weight reduction. Reasonable nutritional goals can be achieved without going to extremes.
To start on a good nutrition program, the basic structure and calorie value of foods need to be understood. Physics texts define a calorie as the amount of energy needed to raise the temperature of a gram of water one degree centigrade; a kilocalorie is the amount of energy needed to raise the temperature of a kilogram of water one degree centigrade. In food science, the kilocalorie is referred to as one Calorie (with a capital ‘C’).
Energy requirements for a day’s worth of activity depend on the amount of work you do, your age, body size and metabolic rate. An average man doing a day’s work in an office uses about 30 Calories per kilogram (13.6 Calories per pound) of body weight; an average women uses about 25 Calories per kilogram (11.4 Calories per pound) of body weight per day. Individuals who have jobs requiring physical exertion have higher energy demands. Most dietitians recommend a balance of 20 percent protein, 30 percent fat and 50 percent carbohydrate for daily energy needs. Table 1 shows the distribution of calories for a 160 pound man and a 110 pound woman, both leading sedentary lives.
The amount of each nutrient in grams is provided for the same calorie distribution in Table 2 (below). If you want to reduce the amount of fat in your diet, you need to replace the calories with another food type. In most low fat foods, the substitute is carbohydrate in the form of sugar, but the proportions often leave you with the same or a greater number of calories. It is ironic that a high carbohydrate diet can cause an elevation of triglycerides (fats) in the blood and can have an effect opposite to what is expected from the diet change.
If you are contemplating a special diet, you should determine whether there is adequate information to justify a large deviation from the recommended balance of foods. Although requirements for essential fatty acids (the building blocks of fat) are only one to two percent of total caloric intake, a very low fat diet may deprive you of these essential fatty acids and cause a loss of normal nutritional requirements. If you are concerned about blood fats and the risk for atherosclerosis, a modest reduction of saturated fat (animal fats and tropical oils such as coconut and palm) in the diet might be reasonable but, in some individuals, excess carbohydrates and fats can raise blood lipid levels.
A long distance runner training daily will require a high calorie intake, which is usually made up of increased carbohydrates.
If you reduce total food intake below your daily energy needs, you will lose weight. This might be the best way to improve your health and reduce fats in the blood, as many overweight individuals have elevated blood lipid levels. Maintaining an ideal body weight by moderation in total food intake, while following the recommended balance of food components, is still the best and safest means of achieving a healthy lifestyle. When you perform a greater amount of work, you can compensate by increasing food intake to obtain additional energy.
To be ready for the demands of diving, you should add an exercise program to your nutritional program. A rough rule of thumb is a mile traveled on foot consumes about 100 calories of energy regardless of the time it takes. A cup of dry cereal or a cup of one percent milk is equivalent to 100 calories. So, a two mile walk will account for most of the calories in your breakfast. If you are aware of your usual daily dietary needs and add as your activity dictates, you should maintain a stable weight and be ready for the physical demands of diving.
FYI: If you would like to review some of the past Diving Medicine articles and other commentary on diving medicine, check out our Web page at www.scuba med.com.
If you are looking for a medical text on diving, the newest edition of our textbook Diving Medicine has just been published (W.B. Saunders, Philadelphia). You can order it through your local book store. The suggested retail price is about $65.
Note: Dietitian Fran Burke, M.S., R.D., provided advice and review for this article.
Safety Recall on Source-12 Batteries: Effective immediately, in cooperation with the Consumer Products Safety Commission (CPSC), Light & Motion Industries, 300 Cannery Row, Monterey, California, has issued a safety warning on all Source-12 batteries purchased between January 1990 and September 1996. If the battery pack floods during a dive, the battery could overheat later while above water and catch fire.
In the event of a flood, it is important to disassemble the retaining ring and bulkhead from the battery, in order to remove the circuit board. By doing so, you will prevent possible ignition of the battery pack. For instructions, contact Light & Motion immediately. Light & Motion Industries strongly recommends you send the battery back for replacement and to discuss lighting upgrade options.
The battery packs, measuring seven by four inches, are black with a clear top and were sold in the following models: SeaHawk Pro Package; SeaBlaze Dual EX; SeaBlaze Single EX; SeaBlaze Single Light; and SeaBlaze Specular Film Light.
Questions regarding the recall can be directed to Light & Motion Industries at (408) 645-1525, fax (408) 375-2517 or e-mail sales@Imindustries.com.