Low Fats, or Low Carbs?

Is there common ground between these two warring camps?

Q: Which rival groups display the most intolerance toward one other?

While politics, religion and sports each create their fair share of bloody rivalries, nothing beats the level of animus generated by differing dietary philosophies.

A case in point would be physicians espousing low fat diets vs. those advocating low carbohydrate diets. The low fat diets, promoted most publicly by Dean Ornish and Nathan Pritikin, stress fat-avoidance and the ingestion of high carbohydrate meals. The low carbohydrate diets, pushed most prominently by the recently deceased Robert Atkins (who died, we are assured, of non-cardiac causes,) stress a radical avoidance of carbohydrates in favor of fat and protein.

Members of each group think they are absolutely and demonstrably right about the best dietary pathway to weight loss and good health, and that their opponents are intractably, thickheadedly, and disastrously wrong. Each group publishes scores of articles and books supporting their respective positions, backed up by scientific studies, and all of these tracts sound quite convincing. What we're left with is two groups of eminent physicians passionately supporting opposite points of view on something as fundamental to health as the optimal diet. So given this state of affairs, what are regular folks - those who just want to know what they should be doing to maintain their health, without sorting through food politics - supposed to do?

This question takes on even more urgency with the appearance of 3 papers from the Women's Health Initiative Dietary Modification Trial, published in the February 8, 2006 issue of the Journal of the American Medical Association, showing that women treated for 8 years with a classic low-fat diet achieved no measurable cardiovascular benefits. This study has embarassed the low-fat diet community, and has left them scrambling to explain these results. No matter how they cut it, however, it appears that the "classic" low-fat diet doesn't do the job it's supposed to do. On the other hand, just the thought of the classic Atkins diet - in which dipping your pork rinds in lard would constitute a perfectly healthful appetizer (prior to the main course of a Porterhouse wrapped in bacon) - is enough to initiate squeezing chest pain.

The purpose of this article is to review - as objectively as possible - information supporting these seemingly opposite approaches to a heart healthy diet, and to try to point out that the low fat and low carb folks aren't quite as far apart as they appear to be. In fact, it is possible to describe several dietary rules that promote both heart health and weight loss, that both groups would, though perhaps reluctantly, agree to.

The low fat case

The folks promoting low fat diets are clearly in the mainstream, inasmuch as they are fully supported by the American Heart Association, the AMA, and the USDA among other prominent health-related institutions. Their position also has the benefit of being eminently logical, and thus intuitively appealing.

Abnormally high levels of cholesterol and triglycerides are clearly associated with cardiovascular risk. Dietary fats - especially saturated fats and trans fatty acids - increase the blood levels of these bad lipids. Further, fatty foods are loaded with far more calories than the same amount of non-fatty foods, and thus lead to obesity - another major risk factor for cardiovascular disease.

It simply stands to reason, then, that strictly limiting the amount of fat (and calories) in the diet should help individuals control both their weight and their blood lipid levels, and there are plenty of clinical studies demonstrating that this is the case. There is some evidence that patients following an extremely strict low-fat diet can experience some degree of reversal of their coronary artery disease. Indeed, proponents of low fat diets simply don't understand all the fuss about the bizarre low carbohydrate diets - low fat is both logical and demonstrably effective. People who think otherwise are simply beyond help.

The low carbohydrate case

If low fat diets are so effective, asks Dr. Atkins and other low carb mavens, then why - after 30 years of promoting low fat diets, and a massive recruitment of the American food production industry to produce low fat versions of every foodstuff - are Americans getting so fat?

It's because a) carbohydrates cause obesity, and b) carbohydrates powerfully stimulate hunger, a fact that leads the poor, unsuspecting victims of the low-fat conspiracy to seek even more carbohydrates.

It works like this: When we eat carbohydrates (especially the rapidly absorbed, simple carbohydrates like sugar, potatoes, pasta, white rice, and anything made from refined flour - you know, the good stuff) we stimulate the secretion of insulin. Insulin causes glucose (the product of carbohydrate digestion) to be rapidly absorbed into the tissues for fuel consumption.

Any "extra" glucose (and the vast majority of the carbohydrates we eat are not immediately needed for fuel, and are therefore "extra" calories) are quickly converted to and stored as - ta da! - fat.

Furthermore, once the glucose levels drop, the insulin levels rapidly fall in turn - and nothing promotes hunger more than a carbohydrate meal followed by a rapid spike then rapid drop in insulin levels. So, 2 - 4 hours after a high carbohydrate meal we suddenly crave (ravenously, desperately,) more carbohydrates - this minute. The cycle repeats, over and over - we eat carbos, store fat, get hungry, and seek out yet more carbos. While assiduously sticking to a low fat diet, we get fat, and as a result our cholesterol levels go up. We die.

That this sequence of events actually occurs (except the dying part, at least not for us, at least not yet) is inarguable. Thus, the scientific basis for the low carbohydrate diet seems at least as sound as that for the low fat diet, to wit: by avoiding carbohydrates, we avoid the spike in insulin levels. Since insulin is the hormone that causes our bodies to make and store fat, then by keeping our insulin levels low we are no longer fat-storing animals, we've changed ourselves into fat-burning animals. Our metabolism actually transforms, so that we primarily use our fat stores for fuel instead of ingested glucose - the fat literally melts away.

One of the nice side benefits of low carb diets is that we can actually measure this shift in metabolism; that is, we can tell whether or not we're in a fat-burning or fat-storing mode. This is because when fats are being burned for energy, byproducts called ketones are released into the bloodstream. These ketones are eliminated in the urine, and can be detected by testing the urine with special dipsticks available in any drug store. If the little brown square on the Ketostix turns purple, you're in the process of getting skinny.

Fewer scientific studies have been conducted with low carb diets than with low fat diets. This is largely because of the incredible prejudice against low carb diets that has grown within the medical community over the past 30 years. (Two generations of physicians have been weaned on the knowledge that fats are bad and carbohydrates are good.) But nonetheless, in recent years randomized clinical trials have been undertaken to assess the effectiveness and the safety of low carbohydrate diets (albeit mostly for the purpose of shutting up the troublemakers pushing those dangerous diets.) Early results from these studies have been surprisingly positive. Not only have low carb diets been shown to be effective weight loss vehicles, but also suggestive evidence has been accumulating that these diets can actually improve cholesterol and triglycedride levels. Serious doctors are finally starting to wonder if there's actually something useful there. Much more data will be forthcoming within the next year or two, but common wisdom has it that Dr. Atkins' untimely demise occurred just as his 30-year quest was about to be vindicated.

Is there common ground?

Mitigating intractable differences

Like Republicans and Democrats, the respective advocates of low carb and low fat diets actually have a lot more in common than appears on the surface. It can be helpful to those of us looking for the "right" diet to examine what those similarities may be.

We can begin mitigating differences in these two dietary approaches right away by stating a truth that neither party can deny: if a person takes in more calories - whether in the form of fats or carbohydrates - than he or she burns up, that person becomes obese. Thus, on one hand, eating lots of low fat food will absolutely make you fat; on the other hand, eating lots of low carb food will also do the same. Dr. Atkins' claim that a person on his diet does not need to count calories (only grams of carbohydrates) is not strictly correct. (That his statement often appears to be true is probably because eating fat quenches the appetite while carbohydrates - as we have seen - can stimulate the appetite, so a diet high in fat can result in fewer calories consumed overall. But the fact remains - if you eat more calories than you burn up, you gain weight.)

Second, in recent years most proponents of low carbohydrate diets have recognized the health benefits of eating certain foods that are relatively high in carbohydrates - especially vegetables and certain fruits. Such foods not only supply necessary vitamins that one misses on a strict no-carb diet, but also supply the "roughage" that aids digestion (constipation, sometimes severe, is an admitted problem with low carb diets) and may help prevent some types of cancer.

Third, also in recent years, even the strictest fat-limiting advocates have had to admit that evidence is now strong that not all fats are alike. Some - the saturated fats and transfatty acids - are bad for you, but other fats - the omega-3 fats and other varieties found in fish, nuts, olives and avocados - are actually healthy, help prevent heart disease, and ought to be included in the diet. Indeed, most low-fat diets - when you look at the small print - now advocate up to 30% of calories from fats, the right kind of fats, of course.

Fourth, the most radical low-fat diets (such as the Pritikin and Ornish diets) strictly limit the same kind of "rapid" carbohydrates (i.e., the rapidly absorbed carbohydrates that stimulate rapid rises and rapid falls in insulin levels) most abhored by the low-carb advocates. Thus, under Pritikin and Ornish, you'll be staying away from the same bread, potatoes, rice and pasta as with the Atkins diet.

Four rules everyone can agree to

At the end of the day, we can state four general rules that all parties - both low fat and low carb - would agree to:

1. Avoid the simple carbohydrates that cause rapid rises and falls in insulin levels - pasta, potatoes, rice, and products made from refined flour.
2. Eat the more complex carbohydrates - vegetables and fruits - that supply necessary vitamins and roughage, without stimulating rapid rises and falls in insulin levels.
3. Eat foods that supply the "good" fats - fish, nuts, olives, avocados .
4. Avoid processed foods of any type that contain transfatty acids - possibly the worst kind of fat you can ingest.

Unfortunately, the low carb and low fat people will always have a few fundamental disagreements. This group adores saturated fats - meats and dairy products - that are the kiss of death to that group. And that group loves the fruits and grains that cause this group to run away screaming.

But for those of us who aren't intent on defending a position - just trying to do what is best - these are differences we can probably live with. These four rules of agreement ought to be enough to get us started. Those, and common sense, should steer us in the right direction.