RAPID WEIGHT LOSS (RWL)
A weekly loss achieved purely from dieting (i.e. by reducing energy/food intake) of more than 1.5 to 2 pounds is regarded as excessive (here to be referred to as rapid weight loss i.e. RWL).
Adverse reactions of RWL range from dizziness, headaches, nausea (and their complications). They become more problematic when the energy intake is less than 1200 Calories and the diet/s nutritionally unbalanced (i.e. deficient in essential constituents).
In addition (and possibly more relevant to the management of body weight on a long-term basis) RWL is invariably linked to the so-called yo-yo effect of dieting.
[Note:
1) The RELIED 500 Cal Plan aims for a weekly loss of 1 pound through a combination of lowered intake (LI) and raised expenditure (RE) of energy (calories).
2) As explained in earlier parts of the Obesity simplex series (to access these, see Archives at the bottom right of this page) this approach is more likely to avoid the yo-yo effect than most].
RESPONSES TO RWL PRODUCED BY CRASH DIETING
1) The body adapts/adjusts to the lowered food intake by lowering its metabolic rate (rate at which the chemical reactions that underpin all life processes take place) thereby lowering its fat usage (“burning”).
[Note: Fat is one source of energy for the body’s activities].
2) This adjustment / adaptation can have disastrous effects best outlined as follows:
a) Imagine someone losing 10 pounds in a relatively short time by going on a diet of quite low energy content (“crash” diet).
[Note: RWL recorded in the early stages of a calorie-restricted diet is to a large extent due to water loss].
b) If food intake is now increased (providing more energy than is required because of the lowered metabolic rate) but is less than before the start of the diet, the body will store the unused (surplus) energy as fat and the weight goes up (“rebound effect”).
[Note: After achieving the initial loss of 10 pounds (achieved by crash dieting for instance) the dieter can now justify increasing their food intake (by what seems to them a reasonable amount)].
The “rebound effect” explains why many dieters try one diet after another and lose weight only to regain it (usually with interest) thereby becoming trapped in weight cycling (the yo-yo effect of dieting).
Perhaps the hardest aspect of the yo-yo effect to ‘swallow’ is that it takes the dieter progressively longer each time to lose weight and progressively faster to regain it (and usually more of it).
From a health point of view there is evidence to suggest (K. van der Kooy and co-workers, 1993) that weight cycling (repeated loss and gain of weight) can increase the risks of diabetes, hypertension, high blood lipids and death.
[Note: The increased risks are no deterrent to genuine attempts at lowering one’s body weight at a sensible rate as mentioned above and throughout the Obesity simplex series].