Straight Talk about Insulin and Weight Loss
Read anything about weight loss published in the last decade or so, and chances are you'll come across plenty of statements claiming that the key to weight loss is to control your insulin levels.
You'll read a lot about insulin "turning off" the fat-burning switch, and that no matter what else you do you won't make any progress if your insulin levels are "out of whack."
Unfortunately, the focus on insulin has left a lot of people confused about what to eat.
One day, for example, you read that coffee raises insulin and makes you fat. So you cut it out of your diet. The next day you read that coffee can actually increase fat burning and reduce the risk of diabetes. So you start drinking it again.
With so many mixed messages, it's easy to feel like throwing up
your arms in frustration and eating whatever you want!
Insulin and weight loss
The truth is that many of the claims about insulin and weight loss are not backed up with any credible research. In fact, studies show that it's possible to lose weight with widely varying levels of insulin.
Let me give you a few examples...
Australian researchers took a group of 33 overweight or obese subjects and put them on one of 3 weight loss diets — low carbohydrate, low fat and high unsaturated fat — for 8 weeks and on the same diets in energy balance for 4 weeks [1].
The only thing the diets had in common was the fact they provided the same number of calories.
And the result?
All three groups lost weight. But those on the low carbohydrate diet lost slightly more weight — 8 kilograms (17.6 pounds), compared with 6.7 kilograms (14.7 pounds) in the low fat group and 6.4 kilograms (14.1 pounds) in the high unsaturated fat group.
The figure below shows the average weight loss in each group over the 12 week study.
Although the low carb group lost the most weight, this was mainly due to the fact that they lost more lean mass than subjects on the other two diets.
In terms of fat loss, which is what most people are interested in, the results show "no significant difference" between groups.
- The low carb group lost 4.5 kilograms (9.9 pounds) of fat.
- The low fat group lost 4 kilograms (8.8 pounds) of fat.
- The high unsaturated fat group lost 4.4 kilograms (9.7 pounds) of fat.
So what does all of this have to do with insulin?
The low carbohydrate diet lowered insulin levels by 33%. This compares to a 19% fall on the high unsaturated fat diet and no change on the low fat diet.
Yet despite these differences in insulin levels, fat loss was virtually identical on all three diets.
If insulin was really so important when it comes to weight loss, you'd expect to see the group with the lowest insulin levels losing the most fat, and the group with the highest levels of insulin losing the least fat.
But this wasn't the case. All three groups lost roughly the same amount of fat.
Similar results are reported in a weight loss study by a group of Stanford University researchers [2].
One of the things they measured was insulin levels at the start of the study, which they then compared with weight loss after 60 days.
If the "insulin prevents weight loss" claim was true, you'd expect to see subjects with low insulin levels losing more weight than subjects with high insulin levels.
Yet the results show something very different.
Insulin levels varied widely from person to person, with an approximately 9-fold variability.
However, as you can see in the figure above, weight loss in absolute terms (left panel) and as a percentage of the initial body weight (right panel), did not vary as a function of differences in the baseline insulin response.
Malcolm Gladwell on insulin
In an article that he wrote for the New Yorker, Malcolm Gladwell — author of books such as Blink and The Tipping Point — picked apart some of the claims made about insulin by Barry Sears, author of "The Zone" series of diet books.
Insulin is simply a hormone that regulates the storage of energy. Precisely how much insulin you need to store carbohydrates is dependent on all kinds of things, including how fit you are and whether, like many diabetics, you have a genetic predisposition toward insulin resistance.
Generally speaking, the heavier and more out of shape you are, the more insulin your body needs to do its job. The Pima have a problem with obesity and that makes their problem with diabetes worse — not the other way around. High levels of insulin are the result of obesity. They aren't the cause of obesity.
When I read the insulin section of "The Zone" to Gerald Reaven, an emeritus professor of medicine at Stanford University, who is acknowledged to be the country's leading insulin expert, I could hear him grinding his teeth.
"I had the experience of being on a panel discussion with Sears, and I couldn't believe the stuff that comes out of this guy's mouth," he said. "I think he's full of it." |
In his excellent book Should I Eat the Yolk, fitness and nutrition expert Jamie Hale also makes the point that the subject of insulin and weight gain has been misunderstood in the fitness industry for years.
Many experts blame obesity on elevated insulin, but the scientific data do not support this claim. Insulin plays numerous roles in metabolism, but popular diet gurus generally have no idea of the complexity and the various effects that insulin has on the body.
"The ability to lose weight on a calorie restricted diet over a short-term period does not vary in obese healthy women as a function of insulin resistance (decreased ability of target tissues to respond properly to insulin) or hyperinsulinemia (high insulin levels)," says nutrition researcher M.R. Freedman.
A review by Freedman, published in Obesity Research, in March 2001, reported that subjects consuming 1,000-calorie diets containing 15 percent carbohydrate had significantly lower insulin levels compared with those consuming 1,000-calorie diets containing 45 percent carbohydrate. Yet there was no difference in weight loss between the two groups. |
Of course, insulin does have a role to play in fat metabolism. But it doesn’t deserve the bad reputation it’s been given over the years, and is really only one instrument in the hormonal orchestra that's playing inside in your body.
Rather than worry about trying to control insulin by micromanaging every last detail of your diet, it's far better to focus on controlling your calorie intake using a diet that you can stick with in the long run.
About the Author
 Christian Finn holds a master's degree in exercise science, is a certified personal trainer and has been featured on BBC TV and radio, as well as in Men's Health, Men's Fitness, Muscle & Fitness, Fit Pro, Zest and other popular fitness magazines.
If you want better, faster results from the time you spend in the gym, click here now for instant access to his step-by-step muscle-building and fat-burning workout routines.
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References
1. Noakes M, Foster PR, Keogh JB, James AP, Mamo JC, Clifton PM. (2006). Comparison of isocaloric very low carbohydrate/high saturated fat and high carbohydrate/low saturated fat diets on body composition and cardiovascular risk. Nutrition & Metabolism, 11, 3:7
2. McLaughlin T, Abbasi F, Carantoni M, Schaaf P, Reaven G. (1999). Differences in insulin resistance do not predict weight loss in response to hypocaloric diets in healthy obese women. Journal of Clinical Endocrinology and Metabolism, 84, 578-581
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