Chapter 32: Fat loss aids
Although there is no magic pill which can cause fat loss without effort, there are
supplements which can be combined with dietary changes and exercise to hasten fat loss and/or
limit muscle loss. These types of supplements work through a variety of mechanisms including
increasing caloric expenditure, preventing a drop in metabolic rate, decreasing the amount of lean
body mass lost while dieting and decreasing hunger when calories are being restricted. Fat loss
aids can generally be grouped into three categories: thermogenic agents, appetite suppressants,
and ‘fat burners’.
Section 1: Thermogenesis and adrenoreceptors
Thermogenesis refers generally to the burning of calories to generate heat which is then
dissipated by the body. There are numerous types of thermogenesis including exercise-induced
thermogenesis and dietary-induced thermogenesis. All forms ultimately cause the body to burn
fuel to produce energy and heat.
To understand the mechanism by which thermogenic agents work, it is necessary to
discuss some of the underlying physiology. This includes a brief discussion of adrenaline and
noradrenaline as well as adrenoreceptors.
The catecholamines: adrenaline and noradrenaline
In response to stress, the body releases two hormones known generally as catecholamines.
They are adrenaline (or epinephrine) and noradrenaline (or norepinephrine). Adrenaline is
released from the adrenal glands and travels through the bloodstream to its target tissues while
noradrenaline is released only from the nerve endings to act on its target tissues (1). Both work
by binding to structures on the cell membrane called adrenoreceptors.
Adrenoreceptors
Generally termed, an adrenoreceptor is a specific receptor on a cell which binds to either
adrenaline or noradrenaline (1). When binding occurs, the adrenoreceptor sends a signal into the
cell causing several reactions to occur. There are two major types of adrenoreceptors: beta-
receptors and alpha-receptors. As well, there are several subtypes of each receptor. They are
discussed briefly below.
There are three primary types of beta receptors known as beta-1, beta-2, and beta-3. B-1
receptors are found primarily in the heart and increase heart rate and blood pressure when
stimulated. B-2 receptors are found primarily on fat and muscle cells and cause the body to