Ryerson University CONTACT | A - Z | SEARCH Student Services
Student Services : Ryerson Health Services : Health Promotion : Health Information : Nutrition - Fad Diets

 


Peer Education Program

Health Info and Links

Games: Activities

Upcoming Events

Ryerson Health Survey
(1993-1994)


Nutrition - Fad Diets

Select a Topic...

  1. High Protein, Low-Carb Diets
  2. Effects of Lack of Carbohydrate
  3. Effects of Excess Ketones
  4. Effects of Increased Fat Intake
  5. Psychological Effects of a Low-Carb Diet
  6. Evaluation the diet books
  7. What really happens when you diet
  8. Word of Advice
  9. Books to check out

HIGH PROTEIN, LOW-CARB DIETS

There are three major nutrients in foods that provide calories: carbohydrate, protein and fat. When you eat a diet low in carbohydrate, it means that you are getting the majority of your calories from protein and fat. Unfortunately, your brain and muscles' preferred fuel is carbohydrate.

Your weight is directly related to the balance between the calories you consume and the calories you expend. If you eat more calories than you burn, those calories are stored as fat and you gain weight, regardless of whether the extra calories came from carbohydrate, protein or fat. Conversely, if you burn more calories than you eat, you lose weight.

A person on a no-carbohydrate diet burns fat, rather than both carbohydrates and fat, for energy; the end product of fat metabolism is the formation of ketones, like acetone. You can tell when a person is burning significant amounts of fats as fuel, because they develop "ketone breath" -- their breath smells like a cross between apples and nail polish remover.

When considering the effects of this type of diet on the body, we have to examine the effects of lack of carbohydrates, the effects of excess ketones, the effects of excess dietary fat intake, and finally the psychological effects of the diet.

The Effects of Lack of Carbohydrates

A low-carbohydrate diet has negative effects on the brain and muscles. The brain works best when it gets its energy from a constant supply of carbohydrates in the form of glucose. If you don't eat enough carbohydrates, the body makes glucose out of the proteins in your muscles, so that your brain can continue to function well -- in other words, part of the weight loss comes from the breakdown of muscle to feed the brain. As a result, the dieter's muscles feel tired, and the person is less inclined than usual to exercise.1

Another point: the by-product of protein breakdown, urea, is excreted by the kidneys. When your kidneys have high amounts of urea to excrete, they must also get rid of water. As a result, the dieter loses water weight. When the dieter has been following a no-carb diet for a while, his or her brain eventually begins to use ketones as a fuel. But the brain isn't as efficient at using ketones as it is at using glucose, so thinking and reaction times are slowed down. The dieter may become lethargic and lose his or her appetite.2

The Effects of Excess Ketones

Excess ketones have many effects on the body, two of which are:
1) Decreased appetite.
2) Loss of body water resulting in weight loss. The scale may trick the dieter into thinking body fat has been lost.3


The Effects of Increased Fat Intake

Low carbohydrate diets restrict grains, fruits and vegetables, while emphasizing meat, dairy and fat. What's wrong with that? Dietary cholesterol is found naturally in foods of animal origin. A diet that emphasizes meat, dairy and animal fats (such as butter) is higher in cholesterol than a diet that includes less of these foods. The fat in your diet (and to an extent your dietary cholesterol) has a direct effect on your blood (serum) cholesterol level and in turn, your risk for heart disease.4

A diet high in meat, dairy and fat is also higher in total fat -- especially saturated fat. A high-fat diet is linked to obesity, heart disease and certain cancers. A diet high in saturated fat also increases blood cholesterol and your risk for heart disease.5

On the other hand, plant-based foods (which are restricted in low-carb diets) are rich in phytochemicals. These substances play a protective role in fighting and possibly preventing diseases such as cancer, osteoporosis, diabetes, and heart disease.

Psychological Effects of a Low-Carbohydrate Diet

A low-carbohydrate diet has adverse effects on the brain, as noted above. In addition, because of the restricted food choice and low variety, the dieter, being tired of eating the same foods all the time, may eat less. (Think of how much of our diet is made up of carbohydrates!) Eventually, most people find such diets too boring and painful to follow, and decide to quit. Unfortunately, many of these people return to the habits which led them to become overweight in the first place, thus setting in motion a never-ending "dieting cycle".


EVALUATING THE DIET BOOKS

The American Institute for Cancer Research (AICR) evaluated four of the most popular diet books:

  • Dr. Atkins' New Diet Revolution (Robert Atkins)
  • The New Beverly Hills Diet (Judy Mazel and Michael Wyatt)
  • Protein Power (Michael Eades and Mary Dan Eades)
  • Suzanne Somer's Get Skinny on Fabulous Food (Suzanne Somers).

According to the AICR, there are several common denominators between all four diets:6

1. All are basically low-calorie diets in disguise. Remember that the only way to lose weight is to eat fewer calories that you spend. There is no magic to it!

2. Because these diets require you to avoid certain foods (and sometimes practically eliminate entire food groups!) they are deficient in such nutrients as carbohydrates, fibre, vitamins, minerals and protective phytochemicals. Dr. Atkins actually recommends enhancing his diet with the supplements he sells!

3. The diets are out of balance, prescribing a dietary intake that is much higher in protein and lower in carbohydrates than what is recommended by Health Canada, Dietitians of Canada, the USDA, the American Dietetic Association, the Surgeon General, the Canadian Cancer Society and the American Institute for Cancer Research, among others.

4. Over the long term, all four diets can give rise to many health risks. By restricting carbohydrates, all four diets lead to an insufficient intake of fibre, which is important in maintaining gastrointestinal health and reducing the risk of some gastrointestinal diseases. The high amounts of saturated fat and cholesterol they prescribe can increase the risk of heart disease, and possibly some cancers. There is recent evidence that a diet featuring excessive protein may leach calcium from the bones, making them more brittle.

5. Two of the diets promote unsubstantiated ideas about "food combinations". Their claim that foods must be eaten in specific orders and at specific times has no scientific basis.

Visit the Center for Science in the Public Interest's website for reviews of the best and worst of the latest diet books. ( www.cspinet.org)

WHAT REALLY HAPPENS WHEN YOU DIET

(Adapted from What Really Happens When We Diet! By the Nutritionists from Boundary Health Unit)
How We Diet What Happens to Your Body
Skipping meals.
  • Lowers your metabolism. In an attempt to conserve energy, your body stores fat more easily from fewer calories.
  • The brain's and muscles' demand for fuel causes rebound "munchies", usually for high calorie foods.
  • Poor attention span, irritability, fatigue.
  • Over the long term, muscle tissue may be lost.
Cut out starchy foods.
  • Your body loses its best source of energy...you'll have less energy and tire more quickly.
  • You may end up eating higher fat and sugary foods to satisfy your hunger.
Cut out meat without getting adequate protein

elsewhere.

  • Iron deficiency may result.
  • Fatigue.
Meal-replacement or liquid diet.
  • You have a 95% chance of regaining any weight you lose in the next year or two.
  • You give away control to the diet, which may affect your self-esteem.
  • You often lose muscle mass along with fat, which results in a slower metabolism.
  • These diets are expensive.
  • Habits are replaced temporarily, not changed permanently.
Fasting.
  • Most weight lost is water.
  • Muscle mass decreases which leads to a slower metabolism and subsequent fat gain.
  • Can be medically dangerous for some individuals.


A Word of Advice

The notion of the "quick fix" is central to all fad diets. Remember that the process of weight gain is usually slow and gradual, and so must that of weight loss. Successful weight loss involves learning new behaviours - it is an ongoing process.

The word "diet" comes from the Greek word "diaita", which means "manner of living". Scientists and dietitians agree that successful weight loss only results from a long-term commitment to sensible eating and physical activity. Your best bet? Meet with a registered dietitian (RD), who will make personalized recommendations based on what fits your life and your preferences. At Ryerson, why not get a head-start by speaking with a Nutrition Peer Educator? S/he would be happy to help you understand the pros and cons of the fad diet you may be wondering about.


BOOKS TO CHECK OUT

•You Count, Calories Don't

Linda Omichinski. Tamros Books Inc., Winnipeg, 1993.

•Intuitive Eating: A Recovery Book for the Chronic Dieter

Evelyn Tribole and Elyse Resch. Saint Martins Press, New York, 1995.

•Breaking the Diet Habit

J. Polivy and C.P. Herman. Basic Books Inc., New York, 1982.


REFERENCES

1,2,3,6 Nutriquest; Cornell's Nutrition Q & A Service. www.nutrition.cornell.edu

4,5 Heart and Stroke Foundation of Ontario. What do sherbet, grilled fish and a whole wheat bun have in common? Pamphlet on dietary fat. CAT 32099222.

<< BACK