Over the last couple of weeks I’ve read a lot of health and nutrition related blogs and discussions out there which are investigating the hypotheses surrounding low-carb in excruciating detail. The following are some of the main areas of contention:
- Is low-carb healthy?
- How does low-carb work – by lowering insulin or by reducing caloric intake?
- Which fats should you eat/Is saturated fat healthy?
Ok, I could go on, but you get the idea. The problem is that in most blogs whenever it comes to topics like that, people will start making elaborate posts that cite studies left and right, and quickly get to a level where it becomes next to impossible for the lay(wo)man to follow the discussion, let alone join it.
That got me thinking about how I’ll be going about with this blog. Am I going to spend hours on posts which reference dozens of studies, talk about levels of hormones and so forth? Nah – there are many bloggers out there who are much better at that than I could ever hope to be. For example, check out Healthy Skeptic.
What I’m going to do is, hopefully, to give summaries of new developments, with my two cents of common sense (with a sprinkling of skepticism) added to it. And to get the whole thing rolling, I’ll give some quick comments on the topics I listed above. Enjoy!
Sure. There are well documented societies that traditionally eat few carbs and suffer no ill consequences. A typical example are the Inuit. Could they be a genetic exception? Probably not. The thing is that when those societies are exposed to Western nutritional concepts (read: starches, sugars), they get the same problems like we do. If they were genetically so different from us that they thrive on low-carb and we don’t, how come that they react to our diet similarly to us? This is not a logical proof – it just shows that it’s not likely.
And there’s also the argument from our evolutionary history. Without going into too much detail: 100,000+ years ago we didn’t have ways to conserve food during winter. Even if you imagine an ice age as extended periods with harsh winters and not full blown artic conditions, our ancestors had to survive for months without any carbs. And when we look at what happens on a low carb diet, indeed we find that our body has mechanisms to adapt – ketosis and gluconeogenesis being the most important ones. Most of our tissue can adapt to burning ketone bodies for fuel instead of glucose (ketone bodies are made by the liver when we starve or consume very little carbohydrate for an extended period of time), and for those cells which need glucose our liver can convert protein and fat into glucose.
How does low-carb work – by lowering insulin or by reducing caloric intake?
This is a huge issue at the moment. In the previous post I comment on Gary Taubes vs. CarbSane – Taubes’s two books are based on “carbohydrate drives insulin drives fat” mantra, while CarbSane, joined by James Krieger, say that at the end of the day low-carb simply works because people involuntarily eat less on a low-carb diet, which is in part due to the satiating effects of protein and fat.
My opinion: It may be a little bit of both. First of all: the people which need to lose a lot of fat are often metabolically different from lean people. They are typically insulin resistant, and even many of those who criticise Taubes would agree that those people may react unfavorably to excessive carbohydrate, and reducing it might be instrumental in normalizing their metabolism – particularly when they’re even diabetic. But independently of all that, on top of it there’s the effect on satiation – and it even gets better. Carbohydrate and sugar are also addictive substances – that’s where the expression “sweet tooth” comes from.
So we have a three-pronged argumentation pro low-carb:
- Metabolism is normalized in insulin resistant persons
- Caloric intake is reduced
- Carbohydrate/sugar cravings are curbed
Now: Does it really matter so much how 1) is accomplished on the level of hormones and lipids? My beef (pun intended) with Taubes’s books is that he makes it look like the mechanism is simply “carbs -> insulin -> fat”, and since this is a gros oversimplification and essentially false, that undermines his position and essentially does low-carb a disservice.
Which fats should you eat/Is saturated fat healthy?
This is a tough one. Saturated fat gets a lot of flak from many camps, including the paleo camp and conventional wisdom. Paleo guys (with the exception of Mark Sisson and Dr. Kurt Harris) don’t like saturated fat because they claim that our ancestors ate very little saturated fat – apparently wild game doesn’t contain a lot of it. But remembering the argument from the first topic about our ancestors and ice ages, that doesn’t convince me. What did we eat in the winter? Game. Or bigger animals, but no matter which ones we ate, those critters accumulate fat in summer in order to make it through the winter. And even when they have less saturated fat than domesticated animals, if they were fatty – and hunter gatherers are known to favor the fattest cuts – we can assume that they got a lot of saturated fat for extended parts of the year.
And what does conventional wisdom say about saturated fat? Right – it clogs our arteries. The fact of the matter though – and here I completely agree with Taubes – is that most saturated fats are either beneficial or neutral when it comes to lipid profiles. Some of them raise LDL (which is the main concern), but they raise HDL along with it. And they change LDL pattern type. But hold on – now I’m about to get too technical. If find LDL pattern types fascinating, but the jury is still out there about whether “large fluffy/buoyant LDL” is really harmless. But do we really need to bother? No. If you haven’t seen the move “Fathead” – do so. Or go to YouTube and look for “Fatheadmovie” and then watch their presentation. The first part of it (and of the movie) deals with how the “lipid hypothesis” was established. Today we’re only looking at our cholesterol levels and lipid profiles because, essentially, of Ancel Keys’s seven countries study, and senator McGovern’s decision to support his conclusions before there was any evidence to do so.
I am not a doctor, and you have to decide for yourself what to do. I don’t take the cholesterol scare seriously anymore.
But I’m going to give you another argument. Imagine you’re going on an extended fast. You only drink water and don’t eat anything at all. What kind of diet are you on?
Answer: A high-fat, low-protein, zero-carb diet. Your body starts to metabolize your lean tissue (protein) and your stored fat, which is about half saturated-fat, half mono-unsaturated fat. So you’ll be on let’s say 40% saturated fat, 40% monounsaturated fat, 20% protein.
Obviously you shouldn’t be doing this for extended periods because ultimately you’ll “waste away”. But you can do like Lyle McDonald advises in his Rapid Fat-Loss Handbook and tweak the diet a little bit: You eat some protein – just enough to get your body to spare your muscle tissue. And it actually turns out that you can keep this kind of diet up for prolonged periods of time, and you’ll lose plenty of fat on it. Your lipid profile will improve, too … even though you’re on a 40% saturated fat diet.
Think about it: Why should saturated fat be bad for you if it is how your body stores energy for later use (or at least half of the energy – remember that the other half is stored as mono-unsaturated fat)? That doesn’t make any sense.
I hope you liked the explanations … please feel free to comment!