There has been a good amount of discussion going on lately about the role insulin plays in the cause of weight gain and its role in the ability to lose weight. The recent discussion has been going on over at My Carb Sane-Asylum such as her posts; Hyperinsulinemia, Hyperglycemia and Insulin Resistance, Insulin Wars V: Dr. Richard Feinman and many others as well as James Kriegers Insulin…an Undeserved Bad Reputation over at his blog www.Weightology.net. I have not read all of the information put out by these two people, but, from what I have, I think they have put forth some useful information and have highlighted some holes in the “insulin makes you fat or inhibits fat loss” thing. With that in mind, I thought I would discuss a couple of papers on the subject.
The first paper is; McLaughlin, T. et al (1999). Differences in Insulin Resistance Do Not Predict Weight Loss in Response to Hypocaloric Diets in Healthy Obese Women. J Clinical Endocrinology & Metabolism; 84(2): 578-581.
I will start with the conclusion and then discuss a few key points. The authors state;
“It is concluded that the ability to lose weight on a calorie-restricted diet over a short time period does not vary in obese, healthy women as a function of insulin resistance or hyperinsulinemia” (p.578).
A few particulars about the study; lasted 60 days, the daily intake of calories was about 1,000 less than estimated daily energy requirements, with 1,200 cal/day being the lowest calorie intake per day, the diet consisted of a commercial liquid nutrition formula plus two high fiber muffins and a sodium supplement daily. The average weight loss at the end of the 60 days was about 20 pounds.
So, overall I think that the amount of weight loss was pretty good. Based on the average of 20 pounds over 60 days, the average weekly weight loss was about 2 ¼ lbs. The women with insulin problems were still able to lose weight at a fairly quick pace and their weight loss was just as good as the women who did not have insulin problems.
I would have liked to see some more specifics of the diet; what was the nutritional make-up of the liquid formula and what was the macronutrient ratios? I would have also liked to have seen an initial bodyfat test done and a pre and post waist measurements to help determine what was lost; fat or muscle? However, regardless of the nutrient breakdown, the bottom-line is that the women with insulin problems who adhered to the diet lost weight just as well as the women who did not have insulin problems.
The second paper; A de Luis, D. et al (2006). Differences in glycaemic status do not predict weight loss in response to hypocaloric diets in obese patients. Clinical Nutrition; 25: 117-122.
Again, I will start with the conclusion. The authors state;
“In conclusion, [the] ability to lose weight on a hypocaloric diet over a 3-month time period does not vary in obese patients as a function of glycaemic status” (p.121).
A few particulars of the study; 3 months long, 1,200 cal/day which had a macronutrient ratio of CHO 51%, Fats 31% and Proteins 18%, 76 obese patients (19 male/57 female).
The average weight loss for the 3 months was 6.16lbs, about 1/2lb per week. The good thing about this study is that they measured body fat and waist measurements. Therefore, it was possible to figure out what type of tissue was lost. It seems that half the weight loss was from fat tissue meaning half the weight loss was from lean tissue. Obviously losing lean tissue is not good. A higher protein intake and a bit of resistance training would likely ameliorate this problem. The other positive change was an average reduction in waist circumference of about 2 ½ cm, which is an indication of visceral fat loss.
The amount of weight loss, for 3 months is on the low side at about 6 lbs. At that pace about 24lbs would be lost in a year. Certainly not bad but at a pace of 1 ½ pounds a week, which is a bit more aggressive but certainly realistic, the amount of weight lost over the year would be about 72 lbs, a big difference. This study, compared to the McLaughlin, T. et al (1999) (see above), had a much lower weight loss. It is likely that there was less compliance to the diet in this study and that is the reason for the lower amount of weight loss.
I think the general conclusion form these two decent studies is that elevated insulin or poor glycemic control will not inhibit weight loss when calorie a deficit is created from a low calorie diet. Based on these two studies and the recent post by My Carb Sane Asylum and James Krieger, the concern about insulin levels and weight loss, the ability to lose weight or not, that is often mentioned by many people in the low-carb community, is probably over emphasized as a key factor for fat loss. However, this does not mean that reducing insulin levels is not a good thing to achieve for health aspects.