How Weight Loss Affects Different Body Tissues, Fat Genes, And Inflammation

(this is fat tissue under a microscope)

We know that a 5-10% weight loss improves many health conditions associated with obesity.  However, it is very interesting to note that some health issues like blood sugar starts to improve with as little as 2-3% weight loss, whereas other health issues like sleep apnea require closer to 10% weight loss before we start to see improvements.  Why is this?


An eloquent study helps us to understand how different tissues in our body respond to weight loss.  This was a randomized controlled clinical trial, assigning 40 patients to a target 0%, 5%, 10%, or 15% weight loss, and then conducted an array of testing to understand the metabolic changes that occur at each of these degrees of weight loss.  Testing was extensive and included assessment of body composition, 24h blood pressure monitors, blood testing for metabolic parameters and inflammatory markers, tests of organ-specific insulin sensitivity, and even biopsies of fat tissue. Participants were weight stable for at least 3 weeks before testing was conducted.

Key findings were truly fascinating.

After a 5% percent weight loss:

• There was a decrease blood sugar, insulin levels, triglycerides, ALT (liver test)
• systolic blood pressure decreased (the top number), but not diastolic (bottom number)
• NO effect on good cholesterol (HDL), bad cholesterol (LDL), glucose tolerance test (OGTT)
• improvement in insulin sensitivity in fat, liver, skeletal muscle 
• improvement in beta cell function (the cells in the pancreas that make insulin)

After 11% weight loss: (the 10% group ended up losing 11%)

• continued reduction in insulin and triglycerides 
• altered gene expression in subcutaneous fat tissue - including genes involved in fat synthesis, cholesterol flux, and inflammation
• no additional benefit to insulin sensitivity in fat tissue or liver
• additional improvement in insulin sensitivity in skeletal muscle
• additional improvement in beta cell function

After 16% weight loss: (the 15% group ended up losing 16%)

• reduction in inflammatory markers (plasma free fatty acids, CRP)
• more marked altered gene expression in subcutaneous fat tissue - including genes involved in fat synthesis, cholesterol flux, and inflammation
• continued reduction in insulin and triglycerides
• no additional benefit to insulin sensitivity in fat tissue or liver
• additional improvement in insulin sensitivity in skeletal muscle
• additional improvement in beta cell function

So what is the BOTTOM LINE from this (rather complicated) study?   

1. A 5% weight loss has important benefits to our health, primarily related to a decrease in our body's resistance to insulin.  

2. Further weight loss continues to improve our body's insulin resistance (particularly in muscle), with additional improvements in our metabolic health.  

3.  At 11% weight loss, we start to see changes in how our fat tissue expresses genes, in favour of better health.

4.  At 16% weight loss, there is a decrease in inflammation in our bodies, and a more marked change in fat tissue gene expression.

While a smaller degree of weight loss (even just 2-3% based on other studies) has a very important impact on our metabolic health, the changes in inflammation and fat gene expression seen at over 10% weight loss may well be what it takes to see benefits in other medical conditions associated with obesity, such as obstructive sleep apnea and arthritis.

Follow me on twitter! @drsuepedersen

www.drsue.ca © 2018

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How Your Diet Influences Where You Lose Fat

In weight management, our goal is to improve overall health.  In a perfect world, it would be preferable if we could melt away the fat around and inside the internal organs (called 'visceral fat') rather than the fat under the skin, as it is this visceral fat that contributes most to health complications of obesity such as diabetes, high blood pressure, and metabolic syndrome.

A recent study suggests that what we eat actually can help us to target this visceral fat.

The CENTRAL study, published in the journal Circulation, randomized 278 sedentary adults with either abdominal obesity or high cholesterol to follow either the Mediterranean diet versus a low fat diet for 18 months.  Six months into the trial, participants were also randomized to follow an exercise program or not. They used MRI scans to evaluate fat under the skin, fat around the organs, fat in the liver, pancreas, and even around the heart.

At the end of the 18 month study, weight loss was the same between all four groups (Mediterranean vs low fat diets, with or without exercise) at -3.2%.   However, where fat was lost from, and how this influenced health, was different between groups:

• People on the Mediterranean diet lost more fat from the liver, pancreas, and around the heart. 
• Exercise with either diet had a greater effect on reducing visceral fat. 

Whether or not total body weight was lost: 

• Losing visceral fat and/or liver fat improved cholesterol.
• Losing fat deep under the skin improved insulin sensitivity.
• Losing fat just under the skin had no effect on health and reduced levels of leptin (a hormone that tells our brains that we feel full). 

The findings that the Mediterranean diet preferentially reduces the more dangerous visceral fat may explain why it is the only diet that has been convincingly found to prevent cardiovascular events.  

These results also show us that it's not about numbers on the scale, as this does not reflect the important changes going on with fat deposit patterns inside. 

Follow me on twitter! @drsuepedersen

www.drsue.ca © 2018

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Why Short Term Weight Gain Can Be Easier to Lose Than Long Term Weight

No weight gained is easy to lose, but - have you ever wonder how Hollywood's actors can gain weight for a movie role, and the next thing you know, they are back at their usual weight for their next photo shoot?  While one may think that it’s simply the superstar access to personal chefs and trainers that gets actors back in shape, there is actually a physiologic basis that can make it less difficult to shed a quick/temporary/intentional weight gain than excess weight that has been present for the long term.

As discussed in a recent Scientific Statement on Obesity Pathogenesis by the Endocrine Society, obesity is associated with inflammation in various tissues, including muscle, fat tissue, vascular system, and liver, and this inflammation appears to be a consequence of chronic obesity.    There is also inflammation in the hunger/fullness centre of the brain, called the hypothalamus.

For a person who has been struggling with weight long term,  inflammation in these tissues causes maladaptive changes in those tissues that make them more resistant to weight loss.    It takes time for this inflammation to develop, so for a person who has had a fairly acute weight gain, it may be easier to drop pounds because they don't have this inflammation working against them.

So then you may wonder - why do some people seem to lose quickly gained weight more easily than others? (e.g. after pregnancy)?

Well, the story of the hunger/fullness centre in the brain is a little more complex.  It turns out that this inflammation may not only be a consequence of long term obesity, but may actually be present in some people before obesity develops.   Some animal studies suggest that eating a high fat diet triggers these inflammatory changes, damaging the neurons in the hypothalamus, which may then result in a disruption of sensations of hunger/fullness, lead to weight gain, plus make it harder to lose it again.

In other words, people who struggle to lose weight after a fairly quick/new weight gain may have inflammation in their hunger/fullness centre that was there before the weight gain, thus making them not only more prone to weight gain, but also making it harder to lose weight than the person without the inflammation. 

Follow me on twitter! @drsuepedersen

www.drsue.ca © 2018

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