carbohydrate but with ‘unlimited’ fat and protein will tend to automatically restrict calories. The
mechanism behind the appetite suppressing effect of ketogenic diets is addressed in more detail in
chapter 7.
Studies examining the ketogenic diet at maintenance calories show no weight loss other
than the small water loss seen with carbohydrate restriction. Simply put, there is no magical
effect of ketosis that allows one to lose weight without some type of shift in energy balance that
leads to either an increased caloric expenditure or a decreased caloric intake. As with any diet,
fat loss on a ketogenic diet will still require the creation of a caloric deficit.
Setting calories for fat Loss
Generally speaking, most dieters restrict calories too much when dieting for fat loss. The
logic is that a greater caloric deficit will yield faster and greater fat loss, but this is not always the
case. Excessively low caloric intakes are countered in the body by a reduction in metabolic rate
which slows fat loss (9,10). This reduction can range from 5 to 36% of resting metabolic rate,
depending on the severity of caloric restriction (9). While the exact cause of the decrease is
unknown, possible causes are a decrease in thyroid hormones, loss of lean body mass, or a
decrease in the activity of the sympathetic nervous system. A similar drop in metabolic rate
can also occur with excessive amounts of exercise. When normal eating resumes, the decreased
metabolic rate causes rapid weight regain, more so if exercise is not included in the fat loss
efforts.
The loss of one pound of fat requires that 3,500 calories be burned in excess of what is
being consumed. Therefore the typical advice to dieters is to restrict caloric intake by 500-1000
calories per day which should yield a 1-2 lb fat loss over the span of 7 days (500-1000 calories/day
- 7 days = 3500-7000 caloric deficit per day = 1-2 lbs of fat loss). As discussed in chapter 22, the
reduction of calories without the addition of exercise will cause muscle loss and metabolic
slowdown. Therefore a restriction of calories should never be the only method of creating a caloric
deficit.
A second approach to creating a caloric deficit is to eat at maintenance calories and add
excessive amounts of exercise. As we will see in chapter 22, the expenditure of even 500 calories
per day with exercise requires a larger amount of exercise (or exercise at a higher intensity) than
most individuals are able to do. To expend 1000 calories per day with exercise generally requires
2 or more hours of exercise per day.
A third and preferable approach is to reduce caloric intake to some degree and increase
activity at the same time. A decrease in caloric intake of 500 calories coupled with an increase in
activity of 500 calories per day should also yield a 2 lb fat loss per week. It is unusual to see an
exact fat loss of 2 pounds per week in most dieters.
How large of a deficit: two common methods
The primary question to be addressed is how large of a deficit to use when setting up a fat
loss diet. As mentioned in the introduction, most dieters tend to drop calories extremely low based
on the idea that the greater the deficit, the more weight that will be lost. Up to a point this