Why doesn't exercise, by itself, aid weight loss? 

There is little evidence to show that exercise, by itself, significantly aides weight loss. This is because high sugar consumption from carbohydrates and processed foods overwhelm our bodies and promote the secretion of insulin. While some sugar is used for energy, the excess is stored as fat.

As we continue to eat carbohydrates and processed foods, our bodies secrete more and more insulin to store sugar as fat. Not only does insulin serve to store fat, it also serves to keep it stored. If fat is "locked up," so to speak, our bodies will crave additional carbohydrates and processed food to provide additional sugar to be used as immediate fuel. As this cycle continues, our bodies compensate by conserving energy and slowing metabolism. Exercise, by itself, cannot often offset this energy conserving state. The nail in the coffin is this: When our bodies are constantly secreting insulin while the fat is "locked up" inside fat cells, exercise promotes the burning of muscles, organs, and other lean tissues of the body to be used as fuel. So even if you do lose weight, it is loss of muscle, not fat. In this way, exercise may have a negative effect, not only on weight loss, but overall health.

What changes in diet are crucial?

Removing, or substantially reducing, carbohydrate and processed food consumption breaks the insulin, fat storing, energy conservation cycle.  Foods that can be safely removed include:

• All grain products
• Bread
• Cereal
• Pasta
• Rice
• All corn products
• All soy products
• Fast food
• Fried food
• "Diet" food
• Bagged, boxed, packaged food

Foods that can be reduced include:

• Fruit (2 servings per day is adequate)
• Starchy vegetables such as potatoes, carrots, and corn

What is effective exercise?

High intensity, short duration exercise energizes the body, speeds metabolism, and taps into fat stores while promoting muscle retention. Exercise should challenge the large muscle groups of the body and last no more than 30 minutes. Workouts lasting more than 30 minutes stress the body and promote energy conservation. In other words, workouts should be invigorating, not overwhelming, long, and fatiguing.

Dr. Cherniawski's comment:

Conventional theory says, if you reduce the calories you consume by eating less and increase the calories you burn by exercising more, you will lose weight. This simply is not true for most people. What's important is what you eat (and don't eat) rather than how much you eat.

Don't be fooled by media or nutritionists who promote carbohyrate consumption as an important part of our diet. While whole grains, fruit, and starchy vegetables are often well tolerated by otherwise healthy people, people struggling to lose weight should drastically cut these and other processed food from their diets. When weight loss goals are acheived, these foods can slowly be added back or, better yet, remain cut.

Source: The American Chiropractor November 2011, Obesity: Why Exercise Doesn't Work, p28-32.