Friday, December 23, 2005

Diet Debates Heat Up and Lead Some to Misrepresentation of the Findings

It's not often I totally rail someone in my blog. Today is, however, an exception.

A dietitian and nutrition consultant in Chicago was a featured writer today at the WTOP radio website with the article, "Taking a bite out of the glycemic index trend." It is, without a doubt, a shining example of how the media misleads when it comes to advice about diet and nutrition because the writer does not do their homework.

In this instance, Ms. Helm, the writer, tackles the increasing popularity of low glycemic index diets and, through carefully crafted buzz words, seeks to convince the reader the approach is worthless and and lacks the 'endorsement' of leading health organizations as a method to control diet for weight loss. In lock-step with the current party-line she believes that this lack of endorsement is some proof that low glycemic diets lack scientific merit and goes on to parrot recent opinions of research findings that claim the results show low GI diets offer no benefit.

Dr. Susan Raatz, a researcher from the University of Minnesota Medical School, who recently published one study, Reduced Glycemic Index and Glycemic Load Diets Do Not Increase the Effects of Energy Restriction on Weight Loss and Insulin Sensitivity in Obese Men and Women, is quoted as saying "Calories are what really count, low GI is not adding any magic bullet to improve weight loss."

Oh really?

I wrote an article about her study October 26, 2005 right here in this blog - Weight Loss: Glycemic Index (GI) and Glycemic Load (GL) - and paid to have access to the full text of her published research data.

Guess what the data showed?

You guessed it - low GI diets did indeed provide a benefit. Too bad Dr. Raatz doesn't have the guts to actually state the facts from her own data!

The benefit wasn't actual pounds lost, even those those who followed the low-GI diet did indeed lose more weight - 1.4-pounds more at the end of 12-weeks. This was just what is known as statistically insignificant. I don't know about you, but if I were trying to lose weight and I lost 1.4 pounds more at the end of 12-weeks, it would matter to me.

But, as I said, the benefit statistically was not actual pounds lost. It was, instead something much more important - those following the low-GI diet LOST LESS LEAN BODY MASS and MORE BODY FAT. And not just a minor difference.

In fact, here is the actual data from the study:

At 12-weeks, the real pounds lost by each group was calculated as:
  • High-GI lost 9.3kg average, or 20.5-pounds
  • High-Fat lost 8.4kg on average, or 18.5-pounds
  • Low-GI lost 9.95kg on average, or 21.9-pounds
At 12-weeks, the lean body mass (LBM) lost by each group was calculated as:
  • High-GI lost 4.8kg on average, or 10.6-pounds of LBM
  • High-Fat lost 2.6kg on average, or 5.7-pounds of LBM
  • Low-GI lost 3.04kg on average, or 6.7-pounds of LBM
At 12-weeks, the body fat lost by each group was calculated as:
  • High-GI lost a total of 20.5-pounds, with 10.6-pounds of LBM, for a fat loss of 9.9-pounds
  • High-Fat lost a total of 18.7-pounds, with 5.7-pounds LBM, for a fat loss of 12.8-pounds
  • Low-GI lost a total of 21.9-pounds, with 6.7-pounds of LBM, for a fat loss of 15.2-pounds
Hello? Anyone home? Which do you think is a healthier weight loss?

Remember, Dr. Raatz said that "Low GI is not adding any magic bullet to improve weight loss."

Losing significantly more body fat and significantly less lean body mass isn't better?

Ms. Helm doesn't stop there though. She moves on to highlight that the committee to revise the Dietary Guidelines for Americans "dismissed" the concepts of the glycemic index, and continued with "reinforcing the notion that "calories in vs. calories out" matters most.

She then takes it a step further to state that the American Diabetes Association has "not endorsed the use of the GI for weight loss." To bolster this, she quotes Marion Franz, an ADA advisor whom Helm writes is a "diabetes expert," who says that "The original intent of the glycemic index is being misinterpreted by the diet books." Franz said the concept of the glycemic index may help people with diabetes "fine-tune" their food choices, but there's little evidence it will enhance weight loss. Most of the weight-related claims - from curbing cravings to increasing energy - are unsubstantiated, she said.

Here, we have an "expert" quote that puts the nail in the coffin of the glycemic index. Not only are we to believe that glycemic index offers no benefit to weight loss, but we're also now to believe that low glycemic index foods will not offer satiety value, curb cravings or increase energy. Add to that the very strong words that such "claims" are said to be "unsubstantiated."

So the overall picture painted is that glycemic index offers no benefit for weight loss, is useless, does not increase satiety, doesn't help with calorie control, will not curb cravings and provides no increase in energy.

You don't have to be a rocket scientist to search, the National Institutes of Health (NIH) database of published research. A cursory search of "glycemic index" and "satiety" returned 37 results.

Within the abstracts we find some interesting statements or conclusions:

Dr. Ludwig: Physiological studies demonstrate that consumption of high GI/GL meals induce a sequence of hormonal changes that limit availability of metabolic fuels in the post-prandial period and cause overeating. Short-term feeding studies consistently show less satiety or greater voluntary energy intake after consumption of high compared to low GI meals.

Dr. Jimenez-Cruz: Eating a lunch with a low GI index resulted in higher satiety perception. These results suggest the need to promote culturally based combined foods with high fiber and low GI. This approach might contribute to the prevention of obesity by increasing the perception of satiety while also improving metabolic control of diabetics.

Dr. Kabarnova: Different metabolic consequences of the intake of individual fatty acids (polyunsaturated and n-3 fatty acids vs. saturated fatty acids), individual carbohydrates (low vs. high glycaemic index carbohydrates) and fibre should be considered during the weight management.

Dr. Warren: The type of breakfast eaten had a statistically significant effect on mean energy intake at lunchtime: lunch intake was lower after low-GI and low-GI with added sucrose breakfasts compared with lunch intake after high-GI and habitual breakfasts (which were high-GI).

Dr. Roberts: We examine whether the consumption of low-glycemic index (GI) carbohydrates may facilitate a reduction in energy intake in obese people attempting to lose weight. Although data from long-term studies are lacking, short-term investigations indicate that consumption of low-GI carbohydrates may delay the return of hunger and reduce subsequent energy intake relative to consumption of higher-GI carbohydrates.

It seems Ms. Helms, Ms. Franz and Dr. Raatz don't exactly hold the same opinion as many of their esteemed colleagues, does it?

So then, what's the real deal?

For one, the research into the usefulness of glycemic index remains open to interpretation.

The approach to managing diet with an eye on glycemic index shows promise yet lacks the clarity we need to effectively establish it as a guideline for consumers. This is due to the fact, as Ms. Helms article states, "[t]he GI ranking of a food also can vary dramatically depending on how you prepare it and how much you eat - which makes it difficult to nail down the actual number." One of the accurate statements in her article.

This lack of clarity is exactly why continued research is critical. We now understand that the glycemic index itself has limitations as a tool. This understanding led to the further research that provided another perspective to consider - the glycemic load. Researchers are finding that the overall dietary glycemic load does indeed play a role in our metabolic response to food and thus our weight and health.

Dr. Jennie Brand-Miller is one of the leading authorities on glycemic index and glycemic load who does research out of the School of Molecular and Microbial Biosciences, University of Sydney, Sydney, Australia. I've met her and can say she's one sharp lady. In a recent letter in Diabetes Care, she and her co-authors provide some great insights:

In their prospective analysis of a cohort of 36,000 adults followed for 4 years, Hodge et. al found that higher-carbohydrate diets were associated with a lower risk of development of type 2 diabetes. However, the type of carbohydrate was equally important: low-GI carbohydrates reduced the risk, while high-GI carbohydrates increased the risk. Thus, low GI and low GL are not equivalent and produce different clinical outcomes.

Because this issue may be confusing to some readers, it is important to clarify the difference between GI and GL. Both the quality and quantity of carbohydrate determines an individual’s glycemic response to a food or meal (2).

By definition, the GI compares equal quantities of available carbohydrate in foods and provides a measure of carbohydrate quality. Available carbohydrate can be calculated by summing the quantity of available sugars, starch, oligosaccharides, and maltodextrins. As defined (3), the GL is the product of a food’s GI and its total available carbohydrate content: glycemic load = [GI x carbohydrate (g)]/100.

Therefore, the GL provides a summary measure of the relative glycemic impact of a "typical" serving of the food. Foods with a GL 10 have been classified as low GL, and those with a value 20 as high GL (4). In healthy individuals, stepwise increases in GL have been shown to predict stepwise elevations in postprandial blood glucose and/or insulin levels (5).

It can be seen from the equation that either a low-GI/high-carbohydrate food or a high-GI/low-carbohydrate food can have the same GL. However, while the effects on postprandial glycemia may be similar, there is evidence that the two approaches will have very different metabolic effects, including differences in ß-cell function (6), triglyceride concentrations (7), free fatty acid levels (7), and effects on satiety (8).

Where I disagree with Dr. Brand-Miller is her caution that, "Our concern is that the use of the GL or "glycemic response" in isolation may lead to the habitual consumption of lower-carbohydrate diets. "

Personally, I don't see a lower-carbohydrate diet as being a problem - especially when I consider the continued publication of research findings that are still showing that a lower (controlled) carbohydrate diet is safe and effective - not only for weight loss, but weight maintenance and management of a host of health issues.

But, I digress...

While this article is lengthy, it highlights how important it is to seek out information for yourself and educate yourself about what the actual data from studies shows. Opinions are not evidence and the article from Ms. Helms is littered with opinions. Not only that, it also lacks support from hard data and a full view of what a broad range of researchers are saying!

Is the glycemic index confusing? Yes

Does glycemic load values make it moreso? Probably

Is such an approach useless, providing no benefit? Absolutely NOT!

What we see here, again, is an article that looks to dismiss the research and get you to just ignore the evidence and get in lock-step with the Dietary Guidelines for Americans. I previously wrote about the same type of call for dismissal by Dr. David Katz from the Yale School of Public Health.

Don't fall for it!

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