Part 2 - Why It Is So Hard To Avoid Weight Regain

In last week's post, I talked about the decrease in energy burn that happens with weight loss.  Today, let's focus on the other major driver of weight regain - the powerful changes in hormones that happen with weight loss, which drive us to eat more and regain the weight we worked so hard to lose.


In humans, there is only one hormone that is known to increase hunger, called ghrelin.  Interestingly, there are many hormones that signal satiety, telling us that we feel full.  Several hormones tell us we feel full in the short term (release 10-15 minutes into a meal), including hormones called GLP-1, cholecystokinin (CCK), PYY, oxyntomodulin, and others.  There are also hormones circulating that are long terms signals of fat and energy storage, which are also fullness hormones: leptin, which is made by fat cells, and insulin, which is made by the pancreas.  These hormones act in the hypothalamus in our brain to regulate when and how much we eat.  (there are also many emotional and social drivers of eating, called 'hedonic' mechanisms... stay tuned for more on this important factor another day :).


When we lose weight, leptin and insulin both drop precipitously, which result in a powerful drive to eat and regain the lost weight.  The short terms regulators of hunger and fullness are affected as well, including a decrease in GLP-1, PYY, and CCK, and an increase in ghrelin, all of which work in concert to beg our brains to eat more, eat more!  Studies have shown that even a year after weight loss, these hormone changes persist - an unrelenting drive to regain the lost weight.

So what can we do to combat these hormonal changes?  It's not easy - evolution has made it so to drive us HARD to look for food and eat during times of food scarcity.  Keeping the energy burn up with activity helps to offset the powerful hormonal drive to increase energy intake, but a whole lotta exercise can be 'cancelled out' by what we can eat in just a minute or two.  Fortunately, medications are now available or in development to combat these hormonal changes, which can help to maintain weight after weight loss.  The only medication along these lines available in Canada is called liraglutide or Saxenda, and it has been shown not only to help people to maintain an average 6% weight lost from diet and exercise, but actually helped people lose an additional 6% weight loss over a year on top of that (with the ever critical lifestyle changes continued throughout).


Disclaimer: I was involved in the research trials of liraglutide as an obesity treatment.  I receive honoraria as a continuing medical education speaker and consultant from the makers of liraglutide (Novo Nordisk). I am involved in research of medications similar to liraglutide for the treatment of obesity and type 2 diabetes.

Follow me on twitter! @drsuepedersen

www.drsue.ca © 2015 

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Why Is It So Hard To Avoid Weight Regain?

One of the biggest challenges in successful weight management is prevention of weight regain after weight loss.   Studies show that most often, people regain weight after intentional weight loss, with many people regaining most or all of their lost weight over time (and then some, in some cases).

There are two major drivers of weight regain:

1.  Many powerful changes in hunger and fullness hormones happen with weight loss, which drive us to eat and regain weight.

2.  Our energy burn (called 'energy expenditure') drops - more than we might expect.

Today, we are going to focus on #2 above. (stay tuned for much more on #1 another day!)


So, just how much does our energy burn drop with weight loss?

Well, it turns out that we are geared towards retaining energy and downregulating metabolism in the face of weight loss, as a strong defence mechanism genetically engineered to protect our weight to survive times of famine.  This happens thanks to a decrease in thyroid hormone levels, decrease in sympathetic nervous system tone, an increase in skeletal muscle efficiency, and other changes as well.  While we do expect a proportional decrease in energy burn simply due to the weight loss itself, the decrease in energy burn is actually much more than that, thanks to these changes.


Here's an example: When a person loses 10% of their body weight, one might think that their daily energy burn (called Total Energy Expenditure or TEE) would also drop by 10%, reflecting 10% less body mass that needs daily care and energy, and 10% less body mass for the person to physically carry around in a day.  In fact, studies show that the total energy burn of this person will actually drop by 20-25%, - in other words - to 10-15% less than what would be predicted.

Said another way, it will take 300-400 fewer calories per day to maintain the 10% loss in body weight, compared to a person of the same body shape, size, and weight, who hasn't lost 10% of their weight.

This decrease in total energy expenditure may not persist forever - the POUNDS LOST study suggested that the TEE comes back up to expected baseline after 2 years (though others have suggested that the reduced energy burn lasts as long as 7 years or more).   Some research has also suggested that the drop in energy expenditure may be less with a low carb diet, higher with a low glycemic index diet, and the highest on a low fat diet (my speculation on this is that this may be related to higher protein intake in the low carb diet - it takes more calories to burn and digest protein compared to carbs compared to fat).

Because of this reduction in energy burn with weight loss, as well as the powerful hormone changes that happen to drive hunger, it is very difficult to maintain weight loss.  Fortunately, the American National Weight Control Registry has provided some useful information regarding habits that help keep the weight off (though these are not easy either) - check it out!

Follow me on twitter! @drsuepedersen

www.drsue.ca © 2015 

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