Low Calorie Diets & Obesity - Functional
Foods
Body Weight Reduction & Energy Balance
The fundamental laws of energy balance dictate that any reduction in energy
intake below energy needs will be sufficient to reduce body weight. This
theoretical framework is supported by numerous laboratory-based studies,
with rigorous control over energy intake, when weight loss occurs in a
predictable manner proportional to the degree of energy restriction. Yet
it is equally clear that in a free-living situation weight loss is surprisingly
difficult to achieve. This suggests that it is not the principle of low
calorie diets that is in question, but how they are implemented.
Body Weight Reduction & Weight Loss
Diets
A number of strategies to decrease energy intake are routinely used in
dietetic practice. This includes the adoption of low fat/high carbohydrate
diets and increased quantities of fruit and vegetables to decrease overall
energy density. Reductions in portion size are often recommended, although
evidence of the efficacy of this approach is limited. In principle decreases
in meal frequency will cut energy intake but the association between snacking
and body weight is complex and confounded by mis-reporting of intake and
post-hoc effects.
Body Weight Reduction & Functional
Foods
Low or reduced energy foods may be considered as some of the first 'functional'
foods on the market, specifically designed to assist weight loss. There
is now reasonably good evidence that high intensity sweeteners induce
caloric compensation and thus are of limited value as a weight loss aid.
However the incorporation of fat substitutes, such as olestra. Into the
diet has usually led to modest reductions in energy intake and a significant
decrease in the proportion of fat in the diet. To date there is very little
data on the long term impact on body weight and even in countries where
its use is licensed the range of products incorporating olestra is so
small that its application in public health terms is limited. Overall
there is little evidence to suggest that isolated low or reduced energy
foods are sufficient for the long term management of obesity. However
they may be valuable when incorporated into the diet as part of a planned
and deliberate strategy to cut energy intake.
Weight Maintenance & Functional
Foods
Functional foods which involve a greater substitution of habitual foods
are more effective. Very low energy diets in which the entire daily food
intake is replaced with a nutritionally complete formula are associated
with significant weight loss, at least in the short term and in individuals
who can comply with the rigours of his type of intervention. However research
is needed to identify an effective dietary strategy for subsequent weight
maintenance. Meal replacement products, in the form of either milk shakes
or cereal bars, that are used as a substitute for one or two meals each
day, can also offer a low calorie option. Recently data from a meta-analysis
over one year of treatment and five-year follow-up data from a community
based self-managed program suggests that this may be a promising approach.
Obesity Treatment
The aim of obesity treatment is two-fold; to decrease body weight and
to reduce the risk of co-morbid disease. The optimal dietary strategy
will reduce energy intake while concomitantly making a positive contribution
to health by incorporating into the diet program foods such as oily fish,
wholegrain cereals, fruit and vegetables. Responsible dietary management
of obesity is much more complex than just cutting calories.
Source: Dr Susan A Jebb, Head of Nutrition
and Health Research, MRC Human Nutrition Research, Cambridge. (2001)
|
com