July 29, 2008

WHI: Low Fat Diet Does NOT Decrease Incidence of Diabetes

The same folks whose multimillion dollar brought you solid evidence that the low fat diet does not reduce heart disease have just analyzed their data and found that eating a low fat diet has no impact on preventing diabetes.

Here's the study as reported by Archives of Internal Medicine:


The Women's Health Initiative Study lasted 12 years and involved 48,835 postmenopausal women aged 50 to 79 years. Women were randomly assigned to a usual-diet comparison group (n = 29 294 [60.0%]) or an intervention group with a 20% low-fat dietary pattern with increased vegetables, fruits, and grains.

Here is the finding: "Weight loss occurred in the intervention group, with a difference between intervention and comparison groups of 1.9 kg [4 lbs] after 7.5 years (P < .001). Subgroup analysis suggested that greater decreases in percentage of energy from total fat reduced diabetes risk (P for trend = .04), which was not statistically significant after adjusting for weight loss." [emphasis mine]

What this means is that whatever tiny difference they found in the incidence of diabetes between the low fat diet group and the group eating a high carb, high fat "eat what you want" diet disappeared when they adjusted their data to take into account weight loss.

People who lost a bit of weight over this period had less diabetes, no matter how they lost the weight.

In fact, we know now that low carb diets produce more sustainable weight loss than do low fat diets. That has been shown in quite a few studies, the most recent of which is the Israeli study that found that a barely-low carb diet (one that was 40% carbohydrate, or 200 grams a day for a person eating 2000 calories a day) produced more weight loss than the low fat diet.

That study is reported here: http://content.nejm.org/cgi/content/full/359/3/229

So if weight loss alone heads off diabetes, the low carb diet would be a much better choice. Of course, the low carb diet (particularly one that is truly low carb, which is not really the case with this Israeli study) prevents diabetes not only by causing weight loss, but by lowering blood sugar to normal levels in people who are pre-diabetic, and by doing this, it prevents the glucose toxicity: the poisoning of beta cells by high post-meal blood sugars, which pushes pre- into actual diabetes.

Sadly, though, the hugely funded WHI study was designed by people who were so certain they would see huge gains from the low fat diet that they did not include an arm that examined other diet strategies. The WHI only compared the low fat/high carb diet with the high fat/high carb diet.

It is worth noting that the Israeli study did not find a significant impact on the development of diabetes in the group of mostly men they studied who were eating a Kosher 40% carb diet. This does not surprise me because these men were eating 200 grams of carbohydrate for each 2000 calories they consumed.

That works out to almost 60 grams per meal--equivalent to a bagel per meal--which would be enough to raise blood sugar damagingly high after every meal for anyone who had any impairment in blood sugar metabolism.

In fact, how this diet could be considered a "low carb" diet escapes me. I would not consider a diet to be low carb unless the carb intake was at most 20% of all calories, or 100 grams a day in a 2000 calorie a day diet, which feedback from a lot of people with diabetes who control their blood sugar using carbohydrate restriction suggests is close to the upward limit of carbs most people can eat and maintain control.

But still, you'd think that the fact that the WHI data show that the low fat diet had no impact on either heart disease or diabetes when compared to the "all crap all the time" typical diet would be the last nail in the coffin of the argument that people with diabetes should cut fat rather than carbs from their diet.

Sadly, it isn't. The American Heart Association and the American Diabetes Association and are funded almost entirely by the drug and device companies and medical groups who earn huge profits only as long people continue to have the diseases these organizations are supposed to be fighting. So as soon as they were published, the AHA denounced the findings of the Israeli study--as tepid as they were, despite the clear cut proof that study gave that the cardiovascular risk profile of people eating a barely low carb diet improved over 2 years compared to those eating the low fat diet.

The ADA is almost certain to ignore the WHI data and say that "more study needs to be done" though the fact is that this was the single largest study of nutrition and health ever funded.

In fact, you can already see how this latest WHI finding was either a) ignored or b) spun by the mainstream media who report it. I've seen at least one report (based on the same abstract you saw at the head of this post) that touted the statistically insignificant difference between the low fat and non-low fat groups as implying that the low fat diet prevented diabetes, when the words "statistically insignificant" mean that in fact the difference in diabetes incidence between the two groups is meaningless.


mollyjade said...

It was a pretty bad study all around. The low carb diet wasn't low carb. The low fat diet wasn't low fat. And there weren't nearly enough women.

Drs. Cynthia and David said...

Fascinating story Jenny. I've never been a conspiracy theory adherent and am reluctant to ascribe malicious intent to pharma and Drs in their inadequate treatments and their bad advice. I agree that the reluctance of the medical profession to accept low carb as beneficial is puzzling. Perhaps it's their egos (not to mention the desire for return on investment, never mind the fact that the science on which current pharmaceuticals is based is all screwed up). And don't forget "cognitive dissonance"- where contradictory evidence just gets ignored in the hope that it will go away! I hope we don't have to wait for an entire generation of MDs and health care "leaders" to die off before we start getting good advice.

Anonymous said...

Interesting story. My reading of the study said that the low-carb group ate 20 gms of carbs per day, increasing to 120 gms per day. Significantly, this study proved that the additional fat didn't hurt weight loss or cholesterol levels. We've seen this time and again, so maybe soon dieticians will exhaust this line, and move on to the carb-blood sugar-diabetes avenue....

Jenny said...

Anonymous, the maintenance phase of the Israeli study was 40% carbs. The group was 80% men. 2000 calories is the lowest you'd put a male on. Do the math and you'll see that 40% of 2000 calories is 800 calories. Divide that by 4 calories per gram of carb and you get 200 grams of carbs.

That is 3+ bagels a day. That is "low carb" only in comparison to a 300 g diet, but not low enough to lower blood sugar!

That it managed to lower cholesterol etc compared the the 300 g diet just shows how damaging the 300 g diet is. But to get diabetes improvement you'd have to drop to 20% or even lower.

Boz said...

When are facts, which are so simple to prove, going to be at the forefront of all the research? That lower carb intake and more exercise are the most effective means to control diabetes in the long run is undeniable. I prove it in my own life every day. Thanks for continuing to expose the frauds out there.

Anonymous said...

I keep carbs below 50 a day..lots of grass-fed beef and okra...BG now stays 91w/walking to 105 w/no walking. Your book was a great help.(hoping to avoid 4th MI)

ItsTheWooo said...

My understanding was they were eating 120 g of carbs per day, and this was the level they were eating regardless of calories consumed? Meaning if they had to eat 2000 cal then fat % would increase because the cals would come from fat. I could be wrong though. Also they were on very low carbs for a little bit of time so that might have helped their metabolism (that's what Dr Eades believes as it is shown in studies extreme low carb intake for a few weeks can protect the body for much longer afterward).

Also, another factor is that people in the general population may underreport their carb intake, just like they underreport calories. So if someone on a diet message board says they eat 100 carbs it might be more like 120 (the more you eat of something generally the easier it is to underestimate amount I find anyway). In the study all food was measured and more controlled so their 120 grams is more acurate.

Anonymous said...

The fact is that eating a well balanced diet will decrease the incidence of diabetes. By cutting refined carbs and minimizing high glycemic grains and vegetables from your diet makes all the sense in the world. Replacing those foods with large amounts of meat and dairy does not - particularly since you can get all of the benefits associated with these diets without the negative side effects. Just:Eliminate the refined and high glycemic carbs; Keep meat consumption to a minimum;Eliminate dairy as much as possible; Include beneficial fats such as fish oil and flax oil; And use lots of nutrient dense foods rich in beneficial carbohydrates and fiber. If you want great recommendations for eating and the miracle grain that seems to have so many people curious, check out a series of newsletters written by Jon Barron titled "Low Carb Craziness". The reads transformed my life and my blood sugar level is normal...finally.

Anonymous said...


I discovered that the low carb diet helped me with my bllod sugar by accident. This was a few years back, when the Atkins diet was the most popular fad on the planet.

I, like many others, experimented with the low carb lifestyle. What I discovered, besides losing weight, was that my blood sugar level was much more stable (and I felt a hell of a lot better).


Anonymous said...

It's bad science to extrapolate the findings from WHI to just anyone, as your blog title does. The WHI study suggests -- science never "proves" anything -- that a lower-fat diet dies not decrease the incidence of diabetes *in postmenopausal women.* While you may be a postmenopausal woman, my husband with type 2 is not, and judging by your readers' comments, many of them appear to fall well outside this category as well. The study makes no observation as to the effectiveness of lowered-fat diet in younger individuals and/or men. And it's pretty bold to take the data from *one* study and make any sort of claim at all.

Jenny said...


I don't extrapolate only from one study. Every single study that has pitted the low fat diet against other diets has shown it to worsen the lipid profile and blood sugars when compared to a diet lower in carbs and higher in fat.

In the large study category there is the Atkins/Ornish/Zone study which found that, and the Israeli study. There has never been a large study that found the low fat diet superior to anything but a very high carb/very high fat diet, which everyone agrees is unhealthy.