Last week I talked about how when trying to lose weight on a low carb diet, you can try to find a sweet spot in terms of caloric intake – you eat enough to ensure that your energy levels don’t decrease while still maintaining a caloric deficit.
By that you can tell that I’m not one of those low carb fanatics who claim that you cannot get fat without eating carbs no matter how many calories you eat, which is my topic for this post. Taubes, Eades and others have made claims that can be interpreted to that effect, and I often encounter low-carbers in forums who argue along those lines.
Let’s examine this in more detail, but without getting into unnecessarily complicated biochemical stuff. The claim is that on a low-carb diet, fat storage is somehow blocked and/or the body either burns off excess dietary fat or disposes of it.
First off: There are undoubtedly people who won’t get fat even when force-fed excess calories. But studies also show that this is most likely a genetic trait, and those people don’t get fat no matter which macronutrients they get force-fed with – even if it’s junk food. Using these people as an indication of what happens when obese people overeat is clearly inappropriate.
About the idea that fat storage is blocked on low-carb diets: Nope. Usually people who think so point to Taubes’s mantra “carbohydate drives insulin drives fat”. This is flawed in at least two ways: a) insulin is secreted even when you eat zero carbs – protein triggers it, too, and protein is a staple of low-carb diets. And b) even when we assume that insulin levels are lower on low-carb diets, there are other pathways to store fat. Sure, type 1 diabetics can’t store fat, but they have zero insulin, which is not the same as low insulin.
When it comes to burning off excess fat, I think this is happening all the time both in lean and obese people. The question is whether this mechanism is ramped up by the body no matter how much we overeat. I don’t think that’s the case – I don’t like the “thrifty gene” theory too much, but on the other hand I don’t think the body likes to waste energy either. My conclusion is that the involuntary increase of metabolic rate in response to excess fat intake can only be effective for small amounts of excess calories, at least in obese people. I also know from first hand experience that stuffing myself with fat quickly reverses fat loss on a low carb diet.
Lastly, what about disposal? Read: Urine or fecies. #1 has been suggested by Eades as far as I remember, the idea is that when you’re in ketosis your body will secrete excess energy that way in the form of ketones. I’m not buying that – some people mentioned that ketones in the urine decrease the longer you are in ketosis. As far as #2 is concerned: I don’t see how the body would put fat back into the lower intestines. Once the foodstuff passes the small intestines, as far as I know there’s no way to add any nutrients back. Besides, if that really worked it could be easily tested and would be a great argument to convince people to go low-carb. Remember Olestra?
On any diet that makes you lose weight, you have to take in less energy than you expend. The latter part is mostly a black box which is far more complicated than many people still think – to them it’s primarily exercise, but there are many more ways for our body to expend energy. But even then, if you eat too much, low-carb or otherwise, your body will store some of the excess calories as fat. Naturally lean people may do so to a lesser degree than obese people – but then again they’re not the ones we should look to as models for how the metabolisms of obese people work.
Then why do low-carb diets work? Studies suggest that they do. The answer may be very simple: People tend to eat less calories when they remove carbs from their diet. Protein and fat are tasty and especially protein helps with satiety. Another bonus is that the fat which low-carbers eat instead of the carbs usually improves health markers – lowering LDL, increasing HDL, lowering triglycerides.
When you go low-carb to lose weight, don’t be obsessive about counting calories – but keep an eye on them. Especially with stuff that’s high in fat – think bacon, butter, heavy cream, olive oil, coconut oil, nuts, avocado – keep in mind that a little goes a long way in terms of both satiety and calories.