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Why Can’t I Lose Weight?
For many of my patients it’s so disheartening to stand on the scales and not see any
improvement despite their best efforts to adapt positive lifestyle changes. They are
told to eat less and move more, but doing so makes no difference. Alternatively, they
can lose weight through changes in diet or exercise but find within a short time of
going back to a normal lifestyle, they are back where they started or at an even
higher weight. These cycles often lead to frustration and helplessness.
What we now know through research is that the body views weight loss as a threat
and has metabolic adaptations to try to regain the weight. Two of the main
mechanisms are discussed below.

Hormones and Appetite
There are many hormones involved in appetite regulation. Two of these are leptin
and ghrelin. Leptin is a hormone that signals satiety, or the feeling of fullness and
ghrelin is a hormone which stimulates hunger. When weight is lost, the levels of
leptin decrease and the levels of ghrelin increase. 1,2 This causes an involuntary
increase in hunger that patients can experience even 12 months down the track,
including if all the lost weight has been regained. 1,2

Energy Expenditure
Studies have also shown that when individuals go through a period of calorie
restriction the body reduces its energy expenditure beyond what would be expected
for the lower body weight. 2 This means to maintain the same weight, an individual
would have to further reduce their calorie intake. This adaptation also persists for
months or even years after the initial period of weight loss, which not only increases
the risk of weight gain, but also makes future weight loss attempts even harder. 2
So, in summary, when you lose weight, the body sends out signals that result in you
feeling hungrier while simultaneously reducing the energy you are burning off. This is
not a personal choice or a failure of willpower, but a physiological response. A lot of
different factors influence weight (a topic for another day), so for some people this
can be overcome with ongoing changes to diet and exercise, but for others it leads to
regaining the weight and starting the cycle again. It is frustrating but unfortunately,
Obesity is a chronic disease, and for many people, it requires a comprehensive
sustainable management plan to counteract this physiological response.

If you are struggling with your weight then please book in with a GP trained in weight
management to discuss your individual circumstances.

References
1. Sumithran P. et al. Long-term Persistence of Hormonal Adaptation to Weight
Loss, New England Journal of Medicine 2011 365:1597-604
2. Rosenbaum M et al; Adaptive thermogenesis in humans; Int J Obes (Lond).
2010 Oct; 34(0 1): S47–S55.