(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.

 

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