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Weight Gain from Forced Overeating has Limits

It seems the only things I can find time to blog on these days are posts from Peter of Hyperlipid. I’ve whittled down the number of blogs I follow that cover nutrition — just not enough time in a day — but Peter’s is fun to read if not a bit “in the weeds.” Peter can go in depth on scientific studies and the chemistry of metabolism, mitochondria, insulin, etc., but he almost always has a way of distilling that information in a way that I can not only make sense of it, but take away some insight. If you are interested in what drives obesity, eating, etc., Peter’s blog is one of the best around. And if you’re not buying the whole “Reward Hypothesis” of obesity that is being trumpeted by Stephen Guyunet (or are at least skepitcal of it — I think Guyunet is off track here; Todd Becker’s theories make a more holistic, coherent case that strings together the behavioral aspects of obesity like reward and the insulin — required reading of his here and here and here).

That’s a big digression from why I’m blogging at all, which is to highlight Peter’s latest, which looks at a study that overfed a few lean individuals by 2000 calories/day and measured their fat gain. What happened? They gained weight, but not as much as you’d predict based on a pure calories in/calories out energy balance theory obesity. Given they were overeating on highly rewarding foods like Snickers bars and chocolate milk, this would seem to fly a bit in the face of the Reward theory of obesity. What’s going on? Well, you have to read Peter, but here’s a taste:

Ah, but if insulin stores fat, why should the level of insulin fall progressively during a sustained hypercaloric eating episode? Surely you must need insulin to store those extra calories? In fact, as insulin levels fall, so does the rate of fat storage. The chaps gained, from Table 3, 1kg of fat mass in the first week and only 0.5kg of fat in the second week… Oh, I guess this must be because the subjects either (a) sneaked off to the gym in the second week or (b) flushed their Snicker Bars down the loo in the second week, without passing them through their gastro intestinal tract first (good idea!) or (c) got bored with Snickers and stopped finding them rewarding. And of course they disconnected their Actiheart monitors at the gym.

Otherwise how you can eat 2000kcal over your energy expenditure, equivalent to nearly 200g of fat gain per day, and gain a kilo of fat in the first week, then continue to eat an excess 2000kcal/d for a second week and only gain half a kilo of fat? Calories in, calories out, you know the rules. Hmmm, in the second week there are 14,000 excess calories-in, 5,000 stored, very interesting. …

[So what is going on here? …]

The mitochondria say they have too many calories. It’s easy for mitochondria to refuse calories from glucose by using insulin resistance, working at the whole cell level. In the presence of massive oral doses of glucose this must elevate insulin to maintain normoglycaemia. The elevated insulin diverts calories from dietary fat in to adipocytes, away from muscle cells. And inhibits lipolysis at the same time … So insulin goes up to maintain normal blood sugar levels, overcomes insulin resistance to run cells on a reasonable amount of glucose and shuts down FFA release to counterbalance its action in facilitating the entry of glucose in to cells.

Core to this is (a) there is no hyperglycaemia, insulin still successfully controls glucose flux and (b) insulin inhibits lipolysis. So you store fat. These subjects are both young and healthy. They do not have insulin resistant adipocytes, mitochondrial damage or a fatty liver. The system works as it should.

As time goes by fasting insulin levels fall and weight gain slows. Calorie intake doesn’t drop. The only plausible explanation is that the subjects generate more heat and radiate that heat during the second week of the study.

Important to the above study was that it was conducted on healthy, non-overweight individuals, so their metabolic systems working “as they should” would make sense — basically, their bodies ultimately start resisting weight gain despite overeating. They heat up and radiate off extra calories.

This makes a lot of sense to me based on my personal experiences overeating—anecdotally it seems to hold water (no glycogen storage = water retention pun intended I swear). Earlier this year I bumped up my caloric intake by at least 4K calories/week (maybe more). Weight gain was incredibly, surprisingly slow after the initial water weight gain as I went from a glycogen-depleted (less water retention) weight to a glycogen-replenished (more water retention weight). It was surprising to me that I didn’t gain more weight overeating, but what I noticed in the process was that I felt like I had more energy, felt warmer, more likely to be active, etc. — this is as compared to alternate day up-day, down-day eating (with a net deficit or close to it) a la I literally felt my body burning off at least some of the caloric excess.

Meanwhile, I paid particular attention to the fact that dietary fat providing calories in excess of my needs would tend to be stored (and made the assumption that excess carbohydrates aren’t easy to turn into fat) so I tended to overeat on carbs and not fat. I think that kept fat gain in check, too.

I’ll wrap with a thought about bodybuilders and a popular diet they use to gain weight — it’s GOMAD, which stands for “Gallon of milk a day.” Nearest I understand it is that you should basically eat your regular diet and then drink a gallon of milk (I believe whole milk is prescribed). The milk provides something like 2,400 of excess calories per day. That’s nearly 17K a week, or if that turned only into fat, it’d be a bit less than 5 lbs./week. I don’t know if this is true or not, but I doubt bodybuilders doing GOMAD actually gain 5 lbs./week. But why even bother with such a huge caloric excess in the first place? Probably because bodybuilders have found — via trial and error and a lot of self-experimentation — that in order to get mass gains (muscle, not just fat), they have to massively overeat to force the body to grow.

Seems our bodies are homeostatic systems and like to keep the status quo. Go figure. Ok, that was probably fascinating to 1% of you and likely .0000001% of the Internet, but I found it fascinating.

Thanks, Peter!

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