a ‘Doc Brown’ moment of euphoria,
the hormone ‘leptin’ was discovered
in rodents (Zhang, Maffei, Barone,
Leopold, & Friedman, 1994). Leptin is
predominantly a fat derived hormone
that circulates in weight stable
individuals in close proximity to fat
mass levels. Cleverly, it communicates
with the hypothalamus.
The importance of this hormone
was demonstrated when humans
and rodents with low leptin levels via
weight loss; demonstrated increased
appetite, suppressed levels of fullness
after a meal, a lower metabolic
rate and calorie burn from exercise
(Rosenbaum & Leibel, 2014). Think
of leptin (there are other hormones at
play here) as a signal to your brain to
preserve what it thinks is necessary to
fend off 5999 (and two thirds) pages of
extended phases of food scarcity and
enable human survival.
Then we have the aforementioned
‘non-homeostatic’ drivers that guide
food intake based on its reward
JUR A S S
SIC PE R K S
value. This system worked a treat
when Captain Caveman scanned the
land for nutritionally rich, calorie-
dense foods. However, today, the
same system spearheads the onset
of obesity by overriding the energy
homeostatic signals in response to
reward signalling (remember the hot
chocolate analogy).
This has been demonstrated in
rodents, who, given an abundance
of their usual bland ‘chow’ diet, will
usually self-regulate their weight
within a close range (even after
bouts of forced overfeeding or caloric
restriction) maintaining homeostatic
order. However, provide the same
rats with a diet of refined fats and
sugar and they become obese and drift
towards a new bodyweight set point.
Their desire to consume such food
persists, even in the administration
of pain (Oswald, Murdaugh, King, &
Boggiano, 2012). The outcomes of the
growth trajectory look to be primarily
down to the luck of the ‘mutation
lottery’, because not all rats (nor all
humans) become obese through
easy, passive overconsumption and
maintain a more robust homeostatic
system.
So, you can see what damage the
‘hot chocolate’ was doing to our
control systems.
But what is the reason behind
weight ‘rebound’ and the systemic
weight loss halt at the six-month
mark?
Well, it appears to be an
overpowering sensation to consume
more calories governed by your ‘inner
hunter-gatherer’ coupled with deep-
rooted reward signals. In other words:
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