A Three-Course Meal -- 3. Dessert: Nutrition, Weight and HIV
Part of A Practical Guide to Nutrition for People Living With HIV
Regardless of HIV status, the equation is simple: Your body weight is a result of how many calories you take in through food and how many calories you use up through all the activities of your day. This equation is called energy balance, and HIV can affect energy balance by increasing the amount of energy used up in the fight against the virus.
Your weight is an indicator of whether or not your energy needs are being balanced by your food intake. In this section we take a look at weight and what to do when weight gets too low or too high.
The body requires fuel each day to have energy to perform all the activities required to sustain life, from the pumping of your heart to your walk in the park. Calories are the measure of energy or fuel that food provides. All foods provide calories: carbohydrates and proteins provide 4 calories per gram and fat provides 9 calories per gram.
REE (resting energy expenditure) is a measure of the number of calories needed by a person when the body is at complete rest. Research has shown that asymptomatic people with HIV have an REE that is slightly increased, by about 10%, because of the widespread effects of chronic inflammation caused by the virus.
Keeping Energy in Balance
Your body weight is an important indicator of your health and nutritional status. Unwanted weight changes can be the first sign that there is an underlying health problem. Weighing yourself once tells you if your weight is in a healthy range, or if it has changed compared to your usual weight. Tracking your weight over time reflects what's going on with your health.
Experts classify people as being underweight, ideal weight, overweight or obese. Different degrees of health risk are assigned to the different groupings. The BMI (body mass index) is one tool you can use to classify your weight. (BMI is calculated as weight [in kilograms] divided by height [in metres] squared.) The BMI has limitations in that it does not factor in gender, age, ethnicity or body composition (see next section). However, it remains the standard for evaluating a person's health risk according to their weight. See Appendix C for a chart that will help you quickly determine your BMI.
The following is the classification system for BMI developed by the World Health Organization. For people living with HIV, a BMI below 20 is considered underweight.
Body weight doesn't tell the whole story about your health. Picture two people, one muscular and one obese, who each weigh the same. Obviously these two people would be in very different states of health. Now imagine somehow being able to separate the different substances that make up your body (fat, muscle, etc.) and weigh each of them. This would give you a useful inventory of what your body is made of -- your body composition. This inventory is often divided into two parts, the total amount of bodily fat, called fat mass, and everything else, called fat-free mass.
Fat is present in the body as essential fat and stored fat. Essential fat is required for normal metabolism and the physical structure of the body. The amount of essential fat is fairly stable and does not change easily. The other kind of fat, stored fat, acts as a reserve of energy, similar to a savings account at a bank. Stored fat is the most variable body compartment: It changes depending on energy balance. Most stored fat is found just under the skin. This is called subcutaneous fat, and it is the tissue that decreases in people who have fat wasting, or lipoatrophy (see "Lipodystrophy," Chapter 5).
Fat-free mass, also called lean mass, can also be subdivided into body cell mass and extracellular mass. Extracellular mass is made up of the body's "inert" parts: water and fluids, bones and structural tissues. Body cell mass includes the muscles and organs. Muscle tissue is the largest reservoir of body cell mass and the most susceptible to change. Because it is critical for survival, a loss of even 5% of body cell mass is considered severe.
Studies have shown that people with HIV sometimes lose body cell mass over time even though weight may stay the same. This is why it's important to monitor your body composition rather than just your body weight and to try to maintain a good amount of muscle mass.
Analyzing Your Body
Weight loss continues to be a difficult problem for people with HIV. Studies have shown that even a small amount of unwanted weight loss increases the chance of getting sick and dying. Whenever weight is lost, some comes from stored body fat and some from lean tissue. How much is lost from those two compartments depends on the underlying cause of the weight loss.
When weight loss is due to not consuming enough calories -- called starvation in medical terms -- about 40% of the weight lost comes from lean mass and 60% from fat. When there is an infectious process with fever, the body develops a stress response to the infection and up to 80% of the weight lost will be from lean mass and only 20% from fat. This is because the body is rapidly breaking down muscle to provide the ingredients needed to fight the infection. This type of weight loss is more serious and more difficult to reverse.
In HIV disease there are many factors that cause weight loss, but not consuming enough calories is generally the driving force. If you have any symptoms or side effects that make it hard to eat, talk with your doctor or dietitian right away. It is important to prevent weight loss and the downward spiral of malnutrition. See Chapter 6 for ideas on how to deal with these and other issues.
The primary strategy for treating weight loss is to increase macronutrient intake to the level needed to promote weight gain. This is achieved with a high-calorie, high-protein diet and a multivitamin-mineral supplement (see "Weight loss and wasting," Chapter 6).
Being overweight or obese is increasingly common among people with HIV, as it is among the general Canadian population. The reasons for this are unclear but may be related to the fact that people with HIV are living longer and better. Obesity -- defined as a BMI over 30 -- comes with its own set of health risks, including heart disease, diabetes, high blood pressure, gallbladder disease, fatty liver disease, loss of bladder control and some cancers. Years ago it was unheard of to recommend that a person with HIV lose weight but it is now clear that the health risks of obesity outweigh the risk of developing wasting in the future.
Losing weight and keeping it off is difficult and takes dedication. There is no shortage of weight-loss diets, and the best ones emphasize healthy, balanced eating that can be sustained over a long period. Many of the so-called fad diets work initially, but they are so restrictive that before long people go back to their old eating habits and regain all the weight they lost.
When considering a weight-loss diet that eliminates food groups or includes only a few foods, ask yourself if this will meet your needs to stay healthy. Rather than "going on a diet," which tends to be short-lived, try to see this as a long-term project for improved health. And think about including some exercise. In fact, the best predictor of long-term success in weight loss is physical activity. Exercise builds lean body mass but most importantly uses energy, which means burning calories.
Working on Weight Loss
Physical activity is a vital part of health and well-being. Maintaining daily activity increases energy, strength and independence and can also help to reduce stress. People who are active and have generous amounts of body cell mass also recover more quickly from illness. Canada's Food Guide recommends getting 30 to 60 minutes of physical activity every day. This does not have to be done all at once but can be added up in 10 minute increments.
The main types of exercise are resistance training (e.g. weight lifting), cardio or aerobic exercise (e.g. swimming or biking), and balance and flexibility exercise (e.g. yoga). Each type has different benefits. Get professional advice on the combination of exercises that is right for you.
Resistance training uses weight to increase body cell mass by building muscle mass. Weight lifting is the fastest way to build muscle but it is not the only way. Resistance exercises can also be done using stretch bands, exercise balls and the body's own weight (e.g. push ups). Muscle burns more energy (calories) than fat, so increasing muscle mass increases the number of calories your body uses up in a day.
Cardio or aerobic exercise, which includes activities like running, walking fast, biking, skating and swimming, benefits heart health and improves insulin sensitivity. This type of exercise promotes weight loss. To get the most benefits cardio needs to be done 3 to 4 times per week for at least 20 minutes.
Balance and flexibility exercises, such as yoga or Tai Chi, help prevent injury and falls and should be included in your exercise program. For more information, read "Let's Get Physical" in the Spring/Summer 2005 issue of CATIE's The Positive Side, available at www.positiveside.ca.
Moving Your Body
This article was provided by Canadian AIDS Treatment Information Exchange. Visit CATIE's Web site to find out more about their activities, publications and services.
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