low fat diets

The Science and Myths of Fat in Your Diet

By Dr. Jennifer Lovejoy, Chief Translational Science Officer

No two individuals are alike, and at Arivale, we analyze important data sets from your DNA, biomarkers, and lifestyle to identify a dietary plan that will best serve you and your goals.

One of the dietary strategies an Arivale Coach might recommend is a low-fat, or perhaps specifically a low-saturated-fat, diet. Pioneers are sometimes surprised about this, saying, “Why would you recommend a low-fat diet? That doesn’t sound very cutting edge.”

Low-fat diets—typically considered to be less than 30 percent of calories from fat—have diminished in popularity over the last 20 years, but there may be good scientific reason to question this trend.

What the research says.

Many decades of research studies—ranging from population studies to clinical trials—have shown that reducing dietary fat, particularly saturated fat, can help reduce risk for cardiovascular disease, Type 2 diabetes and insulin resistance, inflammation, obesity, and a number of other conditions.

For example, studies show individuals who adopt a low-fat diet for only a few weeks significantly improve insulin resistance, a risk factor for Type 2 diabetes.1,2

Another study of a population with one of the highest diabetes risks in the world—Pima Indians—found those living in Arizona eating a high-fat, low-fiber diet had much higher diabetes rates than genetically identical Pima populations living in the Mexican desert eating a high-carbohydrate, high-fiber diet.3

In terms of cardiovascular disease, while there are many studies of benefits of reducing total and/or saturated fat, Dr. Dean Ornish’s study demonstrating a low-fat diet actually reverses coronary artery atherosclerosis is perhaps the most profound—as few non-drug interventions have been shown to have this strong an effect.4

More recently, a large study published in JAMA Internal Medicine found that when compared with the same number of calories from carbohydrate, every five percent increase in saturated fat intake was associated with an eight percent higher risk of overall mortality.5,6,7

So, if all this scientific evidence points to the benefit of low-fat diets, why have they fallen out of favor with so many?

Where we went wrong.

In the late 80s and early 90s, low-fat diets were the rage—everyone was trying to reduce fat intake for weight loss or to improve heart health. Some large food manufacturers responded to the low-fat craze and produced convenient, processed low-fat food.

The problem was lots of processed low-fat food tasted kind of like (well, you know) cardboard. So, food manufacturers added excess amounts of sugar to their low-fat products to help them taste better and sell more. And it wasn’t just food producers causing the problem—being on a “low-fat diet” was an excuse for many to overeat pasta, white bread, rice and fat-free snacks because, after all, these foods don’t contain much fat.

Of course, the results were not good. Replacing dietary fat, or saturated fat, with refined sugar and white flour products eliminates most benefits that would otherwise be gained from a lower-fat dietary pattern.

So, low-fat diets fell out of favor. Atkins was “in” and health professionals touted new research showing that low-carbohydrate diets had multiple health benefits.

 

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And the problem persists.

The media loves to write about nutrition research and, in the process, it sometimes creates a lot of unintended confusion. How many times have you heard someone complain, “I just heard last week that coffee (or coconut oil, or chocolate) was good for me, and now a new study came out saying it’s bad for me!”?

Controversy may sell news but it doesn’t help consumers decide what is actually healthy to eat. Because we are currently in a phase where low-carb diets are popular and low-fat diets are out of fashion, many media stories highlight studies where low-carb or ketogenic diets have shown benefit—as indeed, they do, depending on the outcome one is looking at and what they are being compared to.

Further perpetuating the problem, popular interest can impact research funding and, thus, research publications. It could be fairly difficult for a scientist to secure a grant to conduct a high-quality new study of low-fat diets currently—so it’s not surprising there aren’t a lot of new studies being published on health benefits of low-fat diets.

What about saturated fat?

An example of the challenges of interpreting the science in this area is demonstrated by the controversy around saturated fat. The “butter and bacon are back” message is more ubiquitous in the media than ever, and there are strong proponents of the message that saturated fat, and the higher cholesterol levels that accompany it, are of no consequence in terms of cardiovascular disease (CVD) risk.

This recent movement is compelling at first glance. A few recently published, large studies have concluded there is no association between intake of saturated fat and CVD risk.8,9

One of these studies was a meta-analysis of observational studies reporting associations of saturated fat with all-cause mortality, CVD mortality, incidence of coronary heart disease (CHD), and stroke.8 The researchers concluded that saturated fats are not associated with any of these outcomes. Another popular study was The Minnesota Coronary Experiment (MCE), a randomized controlled trial of 9,423 men and women which concluded replacing saturated fat in the diet with polyunsaturated fat had no impact on CVD mortality, even though it did reduce cholesterol.9

While these studies may seem compelling, they are not representative of the vast majority of research linking saturated fat intake with increased CVD risk. Furthermore, they have also been criticized for containing major flaws.10

Critiques of the meta-analysis cited above show the researchers based their conclusions on selected data rather than the entire set of data.9 Some of the ignored data showed a statistically significant relationship between saturated fat intake and all-cause mortality, as well as with all of the CVD-related outcomes. The ignored data also showed that replacing dietary saturated fat with high-quality carbohydrates such as fruits, vegetables, and whole grains reduced the risk of CVD. Finally, when referring to the MCE trial, many experts have cited major flaws including a significant dropout in subjects (75 percent) due to early discharge, and fake foods created for the trial that were artificially high in omega 6’s, low in omega 3’s, and likely containing trans fats.10

The consensus.

At Arivale, we endeavor to look at all the research that has been published and evaluate it based on the quality of the studies and the breadth of impact across multiple systems. In our research on this topic, it seems clear low-fat or low-saturated-fat diets are likely to have significant benefit for certain Pioneers—including those with high LDL particle number or with significant risk for Type 2 diabetes, as well as some overweight individuals who are genetically predisposed to gain weight on a high-fat or high-saturated-fat diet.

Clearly, low-fat diets are not beneficial for everyone. Some people, depending on their genetics and lab values will likely do best on a more “moderate” dietary fat pattern like a Mediterranean diet or DASH diet.

More important than the “low-fat vs low-carb” debate, though, is the principle that healthy nutrition is not about a single nutrient. Optimal nutrition is about a dietary pattern that is high in whole foods, vegetables, fruits, whole grains, and lean protein, and low in sugar, refined carbohydrates, and fried foods.

Or, to quote Michael Pollan, “Eat (real) food; not too much; mostly plants.” This is something all the experts agree on!


REFERENCES
  1. Fukagawa NK et al. High carbohydrate, high fiber diets increase peripheral insulin sensitivity in healthy young and old adults.  Am J Clin Nutr 1990; 52: 524.
  2. Lovejoy JC et al. Effect of a controlled high-fat vs low-fat diet on insulin sensitivity and leptin levels in African-American and Caucasian women.  Metabolism 1998; 47: 1520.
  3. Schulz LO et al. Effects of traditional and western environments on prevalence of type 2 diabetes in Pima Indians in Mexico and the U.S. Diabetes Care 2006; 29: 1866.
  4. Ornish D, et al. Can lifestyle changes reverse coronary heart disease? The Lifestyle Heart Trial.  Lancet 1990; 336(8708): 129.
  5. Wang DD, et al. Association of specific dietary fats With total and cause-specific mortality. JAMA Intern Med.
  6. Lithander FE, et al. Postprandial effect of dietary fat quantity and quality on arterial stiffness and wave reflection: a randomized controlled trial. J. 2013; 12:93.
  7. Dow CA et al. Influence of habitual high dietary fat intake on endothelium-dependent vasodilation.  Appl Physiol Nutr Metab. 2015; 40(7): 711.
  8. Camhi SM et al. Changes in C-reactive protein from low-fat diet and/or physical activity in men and women with and without metabolic syndrome.  Metabolism 2010; 59(1): 54.
  9. de Souza RJ, et al. Intake of saturated and trans unsaturated fatty acids and risk of all cause mortality, cardiovascular disease, and type 2 diabetes: systematic review and meta-analysis of observational studies. BMJ 2015;351:h3978.
  10. Ramsden CE, et al. Re-evaluation of the traditional diet-heart hypothesis: analysis of recovered data from Minnesota Coronary Experiment (1968-73). 2016;353:i1246.
  11. Hooper L, Mann J. Observational studies are compatible with an association between saturated and trans fats and cardiovascular disease. Evid Based Med. 2016;21:37-37.

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