This is a post to centralize important links on dietary fat and its important role in nutrition.
Fats are Good
One of the most harmful dietary myths that has been entrenched popular thinking for many years is that dietary fat is bad. That paradigm is cracking, with much research over the last 15 years showing the fallacy of that consensus. When studies continued to fail in their attempts to produce evidence for the positive effects of a low-fat diet, saturated fat became the new culprit. As a result, most dietary advice now assumes that saturated fat is “bad fat,” while unsaturated fats are “good fats.” The problem is that saturated fats have never been shown to be detrimental in any scientific study, and the studies now being published are contradicting this theory as well.
Trans fats (which are created when vegetable oils are chemically altered to solidify them), on the other hand, should be avoided based on recent research. You’re far better off eating butter than margarine, which is loaded with trans fats. But what about butter’s high cholesterol content? As it turns out, consuming cholesterol does not appreciably increase one’s blood cholesterol; blood cholesterol is manufactured by the body, not taken in through food consumption.
Another important thing to note in the few “observational studies” typically cited to show eating animal fats (or animal products in general) to be unhealthy are usually conducted by (or sponsored by) people or groups who have an ideological commitment to vegetarianism for other reasons, giving reason to suspect the motives behind these less-than-scientific observational studies. Aside from trans fats, which fat sources should be avoided, based on the best research? Vegetable oils rich in Omega-6 fatty acids should generally be avoided; these oils include regular vegetable oil, corn oil, safflower oil, soybean oil, and cottonseed oil. Ironically, these are the oils often marketed as “healthy” alternatives.
Of course, any talk about the value of fat must be taken within the context of people’s general caloric needs. It’s easier to ingest excessive calories when eating fat, because fat packs more calories into a given volume of food (9 kcal per gram of fat, compared to 4 kcal per gram of carbohydrate or protein).
Still, studies show that it’s actually easier to ingest excessive calories when eating carbohydrates (despite their being less-calorie-dense) because of the body’s hormonal responses to each. So it’s true that excessive calories are “easier” with fat consumption, but they’re also “less likely.” It’s a dietary paradox, but one that makes sense given basic endocrinology.
Basically, this happens because simple (processed) carbs are quickly digested and absorbed into the bloodstream (especially if eaten without much protein or fat) and thus more quickly stored as fat if your body doesn’t immediately need to use that excess blood sugar. Excess blood sugar causes insulin to rise, which causes that excess blood sugar to be stored as fat. And since the digestive system has made quick work of those calories, you feel hungry again quickly, and may just eat more as a result.
Also, moderation in type of fats is still important, as the body uses different fatty acids for different nutritional tasks, and there are some fatty acids termed “essential” (EFA’s) because our body cannot produce them.
New York Times Magazine: “What If It’s All Been a Big Fat Lie?“
This lengthy article looks at the recent work showing weight/fat gain to be closely tied to endocrine responses to sugars, etc., than fat consumption, which seems to help keep people slimmer. It also explores the origins of the “fat is bad for you” myth, tracing things back to a single poorly-constructed observational study by Ancel Keys in the 1950s. It also addresses the impact of all the low-fat diets encouraged from 80s on, suggesting that this dietary experiment may have had a large impact on current obesity problems. It’s a great primer for understanding how popular dietary ideas got so twisted for so long, with a good amount of attention paid to the politics behind the scenes.
WebMD: “The Truth About Fats“
A good look at different types of fats, summarizing much of the recent work done in the field. It still takes a bit of a conservative route with respect to saturated fat, observing that it has never been shown to be “bad” (and saying there’s no reason to avoid it) while still encouraging the reader to focus more on the fats that have been proven to have positive impacts by recent research.
Brad Pilon “Is it time to give up on Low-fat foods?“
A brief but good summary of why the low-fat diet trend was a bad idea.
Tim Ferriss: “7 Reasons to Eat More Saturated Fat“
Just what the title says: why saturated fat is healthy.
Men’s Health: “What if bad fat isn’t so bad? No one’s ever proved that saturated fat clogs arteries, causes heart disease“
This piece starts with Ancel Keys’ observational study and shows that the studies since then have contradicted his “evidence.” It also looks at the latest data on various saturated fats, showing that at worst they have a net neutral influence on blood cholesterol levels. It also explores the various political forces studies showing saturated fat to be healthy have had to deal with—scientific publication is a notoriously political process.
(New York Times) “Good News on Saturated Fat“
Gary Taubes explains the results of recent studies intending to link saturated fat to higher cholesterol and poor heart health, showing that they show no such link.
(Michael Eades) “Another China Study“
This is a very useful analysis of recent observational data from China that contradicts the famous “China Study” (a poorly-constructed observational study often cited to show that saturated fat is “bad”). The study looks at the growing obesity epidemic in China, and Eades shows that the researchers massaged the data to fit their preconceived notions, despite the data contradicting what they were trying to prove. This is a great example of how “science” is not the great objective end to all arguments but is itself controlled by politics and human subjectivity.
Studies related to dietary fat:
Dietary predictors of 5-year changes in waist circumference (J Am Diet Assoc. 2009 Aug;109(8):1356-66.)
This study by the Danish Cancer Society Institute of Cancer Epidemiology ties diets higher in saturated fat consumption (red meat consumption as well) to lower waist sizes, suggesting such a diet would lower the risk of heart disease.
Obesity, insulin resistance, and cancer prognosis: implications for practice for providing care among cancer survivors (J Am Diet Assoc. 2009 Aug;109(8):1346-53.)
This study, from the Department of Nutrition, Food Studies, and Public Health at New York University, “lays out a compelling and detailed map showing how obesity and insulin resistance interact to promote the growth of cancerous tumors. The authors argue that weight loss (if appropriate) should be a central feature of cancer prevention and treatment. Going a step further, the journal’s editors suggest that obesity (and insulin resistance) is the common culprit in all of the Dreaded Three: cancer, diabetes and heart disease” (summary taken from here). combined with the Danish study above, it seems that cancer, diabetes, and heart disease risk can all be reduced by a diet higher in saturated fats and red meat.