Energy: Use It or Gain It

Recently the full picture of fat intake in the diet became more complex. The media seized on a new review of the evidence that suggests saturated fat consumption does not have a causal link to cardiac event risk. What may have been lost in some of the more sensationalized coverage, however, is worth parsing out a bit further here.

With record numbers of Americans developing metabolic syndrome and diabetes, and their well-documented toll on the nation’s health, it’s worth pulling back from any specific debate over saturated fat and acknowledging a wider reality: we eat too much and move too little. Whatever the recent findings specific to what types of fat can and cannot be directly linked to heart attack and other health risks, diabetes and metabolic syndrome are real and they are diseases of abundance. Storing too much energy in the body is bad for your health.

Fat is easy to overeat. At nine calories per gram to protein’s and carbohydrate’s four calories, fat is a readily absorbed and stored contributor to excess weight gain. Regardless of fat type, when we take in more calories than we expend, that energy surplus is stored as fat in the body. Too much of it creates health problems, just as too much glucose in the bloodstream, too often another condition of abundance, causes its own havoc.

Prolonged moderate or vigorous exercise helps the body use its extra sugar stores and also can burn stored fat. It also clears triglycerides out of the blood and dilates the vessels for improved oxygen flow to all parts of the body and lowered blood pressure. These effects can be both acute and chronic. One study of fit runners found that those who exercised vigorously for 40 minutes before consuming a high-fat meal (a fast food breakfast sandwich) cleared one-third more fat from the blood than fit runners who had not exercised first. This seems to indicate that exercising daily as if you are taking a “dose” of it, has the potential, through its acute effects, to deliver a chronically elevated fat-burn in the body. A similarly acute effect has been observed for vasodilation.

While there may be less clear cut evidence than we’d like that saturated fat is inherently bad for heart health, it is still evident that too much fat and sugar in the body leads to major negative health outcomes by simply accelerating people down the path to overweight, obesity, diabetes and metabolic syndrome—particularly sedentary people because they do not experience the above mitigating effects of exercise. As a practical matter, we should be very careful of overconsuming saturated fats, then, regardless of their direct link to any one negative health outcome.

The researchers point out that high-starch, refined (so-called junk) carbohydrates that readily turn into sugar are the real culprit; but this conclusion need not be mutually exclusive from any conclusions about overconsuming saturated fat—overconsuming is the major problem.  There is evidence that “bad” cholesterol (LDL) comes in two types, and the kind found in the bloodstream associated with saturated fat consumption may be the less distressing (the “fluffy” cholesterol molecules, as opposed to the dense, hard ones associated with sugars and refined carb consumption). But any point about consuming too much carbohydrate —more than the body needs for fuel—is a point ultimately harkening back to the problem of too much.   

The current analysis examined prospective, observational studies and randomized, controlled trials using data from MEDLINE, the Science Citation Index, and the Cochrane Central Register of Controlled Trials through July 2013. There were 32 observational studies with a total of over 500,000 participants looking at fatty acids from dietary intake; 17 observational studies (totaling almost 26,000 participants) of fatty acid biomarkers; and 27 randomized, controlled trials (just over 105,000 participants) of fatty acid supplementation.

The authors conclude: “Current evidence does not clearly support cardiovascular guidelines that encourage high consumption of polyunsaturated fatty acids and low consumption of total saturated fats.”

But as The New York Times reported as these findings were receiving wide attention, “A large clinical trial last year, which was not included in the current analysis, found that a Mediterranean diet with more nuts and extra virgin olive oil reduced heart attacks and strokes when compared with a lower fat diet with more starches.”

The concern over starches and sugars emerges from the data on the smallest and densest form of LDL, which, again, is the more dangerous. The Times writes, “These particles are easily oxidized and are more likely to set off inflammation and contribute to the buildup of artery-narrowing plaque. The smaller, more artery-clogging particles are increased not by saturated fat, but by sugary foods and an excess of carbohydrates.”

Still, though the unsaturated fats in foods like nuts, fish, seeds and vegetable oils may be conducive to higher “good” cholesterol (HDL) levels in the blood, they can be overconsumed too, leading to weight gain. But while the evidence may sometimes go back and forth on the exact long term efficacy of unsaturated fat, it never really goes “forth” on saturated fat. That is, this type of fat may not be as harmful as we thought, but it appears to be far from cardioprotective. Since we know that excess weight gain leads to clearly defined health problems, as a practical matter being careful about saturated fat is a good idea. Being careful about fat from fish, nuts and seeds is a good idea too, at the very least by keeping aware of fat servings and recommended intake. But we need some fat, and the latter type, unsaturated fat, has been linked (if a bit inconsistently) to reduced risk of heart disease and certain other problems.

A lack of evidence that saturated fat directly causes heart disease doesn’t really change fundamentally what we ought to be doing dietarily for the best health outcomes. Awareness of the body’s reactions to “macronutrients” like saturated fat is well and good; of greater importance may be a renewed emphasis on a proper balance between energy intake and energy expenditure.

Annals of Internal Medicine, 2014, Vol. 160, No. 6, http://annals.org/article.aspx?articleid=1846638

The New York Times, "Study Questions Fat and Heart Disease Link," by Anahad O'Connor, March 17, 2014,
http://well.blogs.nytimes.com/2014/03/17/study-questions-fat-and-heart-disease-link/?_php=true&_type=blogs&action=click&contentCollection=AsiaPacific&module=MostEmailed&version=
Full&region=Marginalia&src=me&pgtype=article&_r=0

(return to front page)