Why are so many people in first-world countries so overweight? Why is metabolic syndrome so prevalent? The familiar contenders are diet and exercise – more specifically, the wrong kind of each. Both Conventional Wisdom types and nutrition nerds (myself included) agree that we’re doing something wrong in the kitchen and the gym, and that fixing that stuff could solve most of our weight (and even health) problems. Of course, that’s about all we agree on. Specific definitions of “fixing” and “that stuff” remain subjects of vociferous debate. That said, I like when we can agree on something, even if that something is just speculation about another possible factor in the obesity problem. In today’s Monday Musings we’ll take a look at one such factor.
A recent study out of the journal Obesity Reviews notes that it’s not just diet and activity levels that have changed in correlation with rising obesity numbers, but ambient temperature. To be more specific, people are heating their homes at all hours of the day, even as they sleep, and spending less time outdoors exposed to the elements. Central heating is more common, while space heaters, fireplaces, and electric heaters are less common, meaning the entire house gets and stays warm. People in developed countries exist in relative thermoneutrality: a nice 68-72 degrees F. The authors guess that with less exposure to thermal stress, we’re burning fewer calories. Our bodies have an easier time regulating our internal temperatures, and expend less energy doing so.
Insulin is an old, old hormone. Evolution has preserved its structure across hundreds of millions of years and hundreds of thousands of species. Fish, insects, reptiles, birds, and mammals all secrete insulin with fairly similar amino acid arrangements (insulin from certain species of fish has even been clinically effective in humans), so, clearly, it is a vital hormone. But insulin gets a bad rap in our circles. Why? With metabolic syndrome laying waste to the citizenry and with insulin playing an undeniable role, it’s difficult not to be soured on this hormone.
And yet we need insulin to shuttle all sorts of nutrients into cells, like protein and glycogen into muscles. It’s there for a reason, so to demonize it is misguided. It’s chronically elevated insulin and insulin resistance – you know, the hallmarks of metabolic syndrome – that are the problem. You might have noticed a softening stance on carbohydrates around the paleo and Primal blogosphere. I think it’s simply an acknowledgment that in healthy people with healthy glucose control and healthy insulin responses who engage in glycolytic activity, starch is fine in measured amounts. And if insulin increases to shuttle that starch and protein into the insulin sensitive muscle cells, so be it. That’s why it’s there.
But not everyone (anyone?) lives a perfect Primal existence. And even if you did an understanding of how insulin works and what foods and behaviors affect it’s production should be high priority. Especially for the millions of people immersed in the modern, industrial lifestyle, with deranged metabolisms from years of poor eating habits (i.e. most of us).
I’ve always been a bit leery about the overwhelming amount of attention paid to high-fructose corn syrup in the media and among the online health-conscious community. Sure, it’s bad stuff, maybe even especially bad when compared to other forms of sugar, but it is not enough to simply ditch the “corn sugar” and use “healthy cane sugar” (even if it’s evaporated!) instead. Sugar is the issue – fructose. Namely, excessive amounts of it (I’m not going to lambaste blueberries and raspberries) are what you need to avoid. Focusing on HFCS alone and not the general “fructose” is an incomplete and, frankly, counterproductive mode of opposition.
Quick. What’s a suitable, Primal source of post-workout carbohydrates? If the title of this post and the picture to the right didn’t give you a hint then ask your nearest Primal enthusiast and they’ll tell you without batting an eye, “yams and sweet potatoes”. If, for whatever reason, you need some extra carbs “yams and sweet potatoes” is the answer. Everyone knows this, but is it true?
That’s what I’ll be exploring in today’s post. But first, what are yams and how do they differ from sweet potatoes?
Potatoes are controversial in the Primal and paleo world. They represent a bolus of dietary starch, which can wreak havoc on the insulin resistant, but they are undeniably whole, real foods that don’t require much processing beyond simple heating. Grains and legumes, on the other hand, are tiny, disparate sources of calories that need soaking, fermenting, and extensive heating to be palatable (and they’ll still mess you up), but potatoes are big, dense, and obviously food. Chimps have been known to use sticks to dig up and eat wild tubers, and they’ve got even less salivary amylase to break down starch than we do. Evidence exists for human consumption of roots and tubers from multiple sites spanning multiple time periods: Northern Europe (specifically Poland), in the terminal Paleolithic and early Mesolithic. Clearly, we have the physiology (amylase production, glucose metabolism), the tools (fire, hearths, digging implements), and the motivation (attraction to dense caloric sources with negligible or easily neutralized anti-nutrients) to consume starchy tubers.
So what’s the hold up? Why do I generally recommend limiting their intake?
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