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Low-carb diets: the skinny on saturated fat

This is an excerpt from Diet Lies and Weight Loss Truths by Melody L. Schoenfeld & Susan M. Kleiner.

Many low-carb gurus tout the benefits of saturated fats, explaining that they are not harmful to health like we always believed. When the sources of saturated fats and other lifestyle and dietary aspects are not considered, studies do demonstrate that they are, in fact, pretty benign (25-27).

The issue becomes muddier, though, when we consider what the saturated fat is replaced with. A Western diet, for example, tends to be high in refined carbs, trans fats, and sugars. If you compare a diet high in saturated fats to a Westernized diet, like the one I just mentioned, the saturated fats without junk foods will demonstrate a lower risk of heart problems and other diseases (26-29). But when a diet high in saturated fats is compared to one high in monounsaturated or polyunsaturated fats like omega-3 and omega-6, the risk of disease is much higher for saturated fats (26-27). When saturated fats are replaced with unprocessed, complex carbs like vegetables, beans, and whole grains, the risks also decrease (28-29). Saturated fat coming from milk and cheese may lower the risk of heart disease more than that coming from meat, but unsaturated fats still reign superior to either kind of saturated fat (29-30). Replacing animal-based saturated fats with protein—particularly plant protein—also appears to possibly reduce the risk of heart disease (29-30). Furthermore, the body naturally produces its own saturated fats; it is unnecessary to consume them. The bottom line is that there is no biological need to eat saturated fats; when it comes down to consuming them, it’s not just about reducing saturated fats—it’s about replacing them with something healthier.

Weight Loss Versus Fat Loss

One issue with many studies is that they concentrate on weight loss rather than fat loss. These two things are not quite the same. Your body’s weight does not reflect your body’s composition. (I’ve seen my own weight fluctuate up to 10 lb in a day, depending on what I ate and what time of the month it was.) Weight loss on a low-carb diet can often be explained by water loss—carbs are converted to glycogen in the body, and glycogen stores a couple of grams of water along with it. When your carb intake is low, your body starts to use stored glycogen as fuel, which means it will shed the stored water along with it. It’s a pretty cool trick I’ve used for powerlifting if I needed to make weight for a competition. The week before the competition, I’d cut way down on carbs. I’d be grumpy and miserable, but by weigh-in time, I’d be a few pounds lighter. Then I’d eat a sandwich, and all would be well again. That isn’t to say that low-carb diets don’t cause body fat loss; the available information shows that they do, comparably to other popular diets. But any edge in weight loss might be explained by water loss, and this water loss phenomenon does not last for the long term.

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