Fad Diets Analyzed

From Today's Chiropractic ~ March 2004

By Jaleh Dehpahlavan

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In the last edition of Today’s Chiropractic, we summarized some of the popular diets and weight management programs. In this edition, we will examine the scientific pros and cons regarding low carbohydrate, high protein diets such as the Atkins and South Beach diets in managing our weight and achieving optimal body composition. In order to understand the principles of weight management, we will first review the basics of Basal Energy Expenditure (BEE) and Total Energy Requirements (TER), which include BEE and energy requirements for external activities. We will then discuss a few tips for safe and permanent weight management.

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Principles of Weight Management

Optimal weight, which is defined as a Body Mass Index (BMI) of between 18.5 and 25, or between 10 and 20 percent body fat for males and 20 to 30 percent for females, can be achieved mostly through the balancing of energy intake with energy expenditure. Energy intake comes from intake of carbohydrates (four calories per gram), protein (four calories per gram) and fat (nine calories per gram), and of course, alcohol (seven calories per gram). Energy expenditure includes Resting Energy Expenditure (REE), which is the amount of energy required for the body to function in a state of rest. REE depends on the size of body, amount of lean or fat mass, age, gender, thyroid gland activity, body temperature, health and disease status and environmental temperature.

Mahan and Escott-Stump (2004) estimate the REE accounts for up to 60 to 70 percent of the total energy expenditure per day. The other major energy expenditure is the amount of energy required for physical activities. The amount of energy required for physical activity also relates to body size, age, and lean or fat mass. To achieve and maintain optimal body weight, it is essential to balance these two types of energy requirements. If one takes in more energy than one expends, the extra energy will be stored as fat, which leads to an increase in the BMI and percentage of body fat. On the other hand, if one consumes less energy than one expends, then the body will utilize the fat stored, thus reducing BMI and percentage of body fat. This is a fact that has been confirmed over and over again. Just looking at societies whose members have to engage in daily physical activities, such as walking to the bus stop or underground station, or third world countries whose members do not have the luxury of taking in a large amount of food per day and have to endure some daily physical activities, shows that obesity is not a problem at all.

So, if it is that easy to balance food intake with physical activity, then why do people have such a hard time losing weight and keeping it off? In today’s society, especially in the United States where the existence of machinery has reduced the need for physical activity and where food is available and the serving sizes are huge, people have a hard time balancing their energy intake with their energy expenditure. Another factor contributing to the difficulty in balancing energy intake with energy expenditure is that the composition of the food is now higher in refined and simple carbohydrates which results in quick absorption, thus causing hunger urges which, in turn, lead to more consumption. Due to these reasons, some people have a difficult time balancing their energy intake with their energy expenditure and they become obese.

The trend of increasing obesity has continued in the United States over the last few decades in spite of known detrimental consequences, such as development of hypertension, high serum cholesterol, cardiovascular disease, type II diabetes, and many others. Bravata, Sanders, Huang & Krumholz (2003) state that over the past 40 years the incidence of obesity has risen sharply from 13.4 percent of the population in 1960 to 30.9 percent of the population in 2000. They further state, “An estimated 325,000 deaths and between 4.3 and 5.7 percent of direct health care costs (approximately $39-$52 billion) are attributed to obesity annually”.

A number of ways have been suggested to treat obesity, including surgery, medication, and of course, numerous types of diets and weight management programs. Low carbohydrate, high protein diets have gained a lot of attention in recent years. Do these diets work—and are they safe?

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Low Carbohydrate, High Protein Diets

The Atkins diet, which restricts carbohydrate intake and prescribes high protein intake in order to lose weight, was developed by Robert Atkins about 20 years ago. He was a cardiologist who believed that a high protein diet would facilitate weight loss and improve serum cholesterol and thus reduce the incidence of heart disease and other complications associated with excess body weight.

Atkins (1992) believed that his diet works because it limits production and excretion of insulin, an anabolic hormone, which does not promote fat oxidation when elevated, whereas the lack of insulin leads to mobilization of body fat for production of energy, as evidenced by the increased production of ketone bodies. He argued that the increased production of ketone bodies also reduces appetite, which allows for better weight maintenance. Although he never conducted a scientific study to prove that his diet works and is safe, he used his patient cases in his bestselling book, Dr. Atkins’ New Diet Revolution, as evidence that his diet works. So, does the diet work as claimed?

Bravata, et al. (2003) attempted to answer this question by conducting a meta-analysis study. In this study, the authors examined 107 studies published from 1966 through 2003 that dealt with low carbohydrate (20-60 grams per day) and high carbohydrate (greater than 60 grams per day) caloric restricted diets. The majority of the studies had a randomized research design with a control group. The dietary variables included the grams of carbohydrate, fat and protein and total calories that were given to participants per day. Another variable was the duration of dietary intervention or the number of days (4-90 days) which the participants received the intervention. The participants’ variables were age, sex, BMI, serum lipid levels and glycemic control such as blood glucose and insulin level. The participants were divided in two groups, with one group receiving a low carbohydrate, high protein diet and the other group receiving a caloric restricted, high carbohydrate diet.

The conclusion of this study indicated that the higher weight loss was achieved by the participants who had a lower caloric intake and were on the diet for a longer period of time, but there was no correlation with reduced amounts of carbohydrate intake. Furthermore, the authors found that low-carbohydrate diets did not have any adverse effects on fasting serum lipids, glycemic index or blood pressure. The authors then concluded that they could not draw any conclusions for or against low carbohydrate diets.

Brehm, Seely, Daniels, & D’alessio (2003) conducted another study, titled “A randomized trial comparing a very low carbohydrate diet and a caloric restricted low fat diet on body weight and cardiovascular risk factors in healthy women.” For this study, 43 obese females were randomly assigned to either a carbohydrate restricted diet or a caloric restricted low fat diet in which the total calories for both groups were comparable. Body composition, blood pressure, and fasting blood glucose were measured at baseline, at three months, and at the end of the study at six months. Each subject was also given an electrocardiogram during each of these three test intervals.

The results clearly indicated that the subjects on the low carbohydrate diet lost more weight (8.5 lbs) and body fat than the subjects on the restricted low fat diet (4.8 lbs). The other measurements were within the normal range at the baseline, however, the lab data showed improvement at the three-month interval and the six-month end of study interval. The authors of this study concluded that the low-carbohydrate diet is more effective in promoting weight loss than the low-fat diet for a short period of time. They also concluded that the low-carbohydrate diet does not have adverse effects on the cardiovascular system in healthy women.

So, this last study indicated that the low-carbohydrate diet can be more effective in initial weight loss and both of the studies indicated that a low-carbohydrate diet does not have any adverse effects on health during a short period of time. Of course, neither of these studies discusses the side effects of low fiber with this kind of diet. Fiber, which is the nondigestible part of complex carbohydrates that is fermented by the bacteria of colon, is not only necessary for the healthy function of the gastrointestinal tract; it has also been linked to the reduced risk of colon cancer (Lieberman, Prindiville, Weiss, Willett, 2003). The other problem with this kind of diet is that too much protein can increase excretion of calcium, and thus, cause bone damage. Reddy, Wang, Sakhaee, Brinkley & Pack (2002) demonstrated that in human subjects who received a high protein diet, urinary calcium excretion level increased from 160 mg /dl to 258 mg/dl, an almost two-fold increase in calcium losses, which can led to bone demineralization. High intake of fat has also been associated with increased risk of some types of cancer, which may not be seen with the above studies since the study durations were short.

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Permanent Weight Management

As mentioned before, to manage one’s weight there must be a balance of energy intake and energy expenditures. The energy expenditures can be increased by incorporating physical activities. Physical activities, both aerobic and weight lifting, are not only essential components of weight management by increasing lean muscle mass, they also have a number of other benefits. These include improving serum lipids and thus reducing the risk of heart disease, improving bone density, and relieving stress, to name a few.

Most importantly, make physical activity a routine part of your life. Start with small activities that you enjoy and then slowly increase the duration and level of difficulty. Other activities that can increase your energy expenditure include gardening, household chores, walking to places instead of driving, and using stairs instead of elevators when you can.

To reduce energy intake, be aware of portion size and select smaller portions of food. Eat more frequently, smaller meals so that you avoid overeating. Limit or restrict your intake of food made from simple carbohydrates such as cakes, cookies and candies, to name a few. If you crave high calorie foods, go for it, but take smaller portions and share it with your family and friends. Eat slowly and enjoy your meals and snacks. Plan your mealtime and snack time so you do not do anything else simultaneously and you are aware of what you are eating. Incorporate fresh fruit, vegetables and legumes in your daily diet and, finally, drink plenty of water (between six and eight 8-ounce glasses per day).

In summary, weight management requires deliberate action of balancing energy intake with energy expenditure. To achieve optimal BMI or percentage of body fat, one must be aware of what is taken in as a source of energy. This is important in preventing obesity and the side effects associate with obesity. There are a number of diets and weight management programs that claim to cure obesity and help you maintain your weight, but remember that moderation is the key to enjoying life and, at the same time, maintaining your weight. The low carbohydrate, high protein diets have gained a great deal of popularity in recent years, and although the studies that were reviewed indicated that these diets may be beneficial, the long term safety and efficacy of this diet is still questionable.

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Jaleh Dehpahlavan is the chair of Life University's Nutrition Department.

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References:

Atkins, R. C. (1992). Dr. Atkins’ New Diet Revolution. New York, New York: Avon Book Inc.

Bravata D. M., Sanders L., Huang J., & Krumholz, M. (2003) “Efficacy and safety of low-carbohydrate diets: a systematic review.” Journal of American Medical Association, 289, 1837-1850.

Brehm B. J., Seely R. J., Daniels S. R. & D’alessio, D. A. (2003). “A randomized trial comparing a very low carbohydrate diet and a calorie-restricted low fat diet on body weight and cardiovascular risk factors in healthy women.” Journal of Clinical Endocrinology Metabolism, 88, 1617-1623.

Lieberman, D. A., Prindiville, S. Weiss, D., & Willett, W. (2003). “Colorectal cancer, risk assessment.” Journal of American Medical Association, 290, 2959.

Mahan & Escott-Stump (2004). Krause’s Food, Nutrition & Diet Therapy (11th ed.). Philadelphia, Pennsylvania: W. B. Saunders Company

Reddy, S. T., Wang, C. Y., Sakhaee, K. Brinkley, L., & Pack, C. Y. (2002). “Effect of low carbohydrate high protein diets on acid base balance, stone forming properties, and calcium metabolism.” American Journal of Kidney Disease, 40, 265-274

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