cgcrutch wrote: »

I'm finally losing! I guess the fast helped kick start ketosis, I'm down another pound and a half since the fast

Another diabetes risk factor that has shown a sex-specific effect is glucose tolerance. After 3 wk of ADF (Alternate Day Fasting), women but not men had an increase in the area under the glucose curve. This unfavorable effect on glucose tolerance in women, accompanied by an apparent lack of an effect on insulin sensitivity, suggests that short-term ADF may be more beneficial in men than in women in reducing type 2 diabetes risk.

“At the end of the trial there was no insulin improvements in the women and their glucose response got worse, while the men had no glucose changes and their insulin response improved.”

American scientist, author and blogger Stefani Ruper, who was one of the first to question the safety of the 5:2 regime, warns: “The IF regime was not just neutral for women, but was downright harmful.”

People started commenting that they were doing great on the IF. Some were losing weight, but others weren’t. Or if they were, they were losing much less than they thought they should be losing given the caloric reduction. As I mentioned, it seems that humans have a difficult time doubling up on calories on eat days, so in most humans an IF is also a reduced-calorie diet. And humans, it appeared, weren’t losing as much as their reduction in calories would predict. Reports started popping up on low-carb bulletin boards describing how blood sugar levels had gone up in people IFing and how some people had seen their blood pressure go up.

Like many of my readers, the research community had jumped on the IF bandwagon as well. And, in a similar fashion, the results were not all positive. Papers appeared showing that subjects IFing, or even regularly skipping a couple of meals per day, were developing insulin resistance, impaired glucose tolerance, elevated blood pressure, and decreased thermogenesis. Even Mark Mattson published a couple of human studies, including a randomized crossover designed experiment that showing the above disorders in women who ate the same number of calories in one meal per day as opposed to three meals per day.

I must hasten to add that the loss of insulin sensitivity, the impaired glucose tolerance and high blood pressure did not reach major levels. But they were significantly more pronounced than the same measures in the same subjects consuming the same number of calories divided into three meals instead of just one. The finding that troubles me the most, however, is the decrease in thermogenesis found under iso-caloric conditions. Said decrease in thermogenesis can only be worse in a true, real-world, intermittent fast in which the calories are typically lower than usual.

The decreased thermogenesis explains why the IF doesn’t work particularly well as a weight-loss regimen even though in most cases it is a reduced calorie diet [see the “the real science of fat-loss: why a calorie isn’t always a calorie” post for more on this phenomenon]. The subjects in these studies who consumed only one meal per day had reduced thermogenesis even while consuming the same number of calories that they did when eating three times per day. Imagine the reduction in thermogenesis if the calories were reduced as well as they are in most IF regimens.

The energy balance equation states that the change in weight equals calories in minus calories out.

Δ Wt = kcal in – kcal out

Many people think that the items on the right side of that equation are independent variables. In other words, if kcal in decreases weight will be lost because kcal out stays the same. But it doesn’t work that way because those terms aren’t independent variables – they are dependent variables. If kcal in goes down, often kcal out goes down as well to compensate. If people increase kcal out by exercising, they end up increasing kcal in because they eat more.

It’s looking like the intermittent fast is another of those ideas in science that looks good in animal studies then not so good in human studies, proving once again that rats and mice aren’t simply furry little humans. And it appears – for humans, at least – that the intermittent fast is indeed beginning to look like the reality of a late-night gimmicky infomercial: long on promises, short on delivery. I suspect that it is also a cautionary tale about the applicability of caloric restriction studies to humans.

Sorry to be the bearer of bad news, but that’s the way science sometimes works. Lab results and reality are often two different animals.

tcunbeliever wrote: »

Autophagy is happening all the time at varying levels. It's going to kick in high gear once liver glycogen is depleted, which is pretty much all the time with a keto diet. It's going to kick into high gear after about 12-24 hours of fasting. It's also going to kick in high gear with exercise, though possibly not high enough to offset the damage from exercise, depending on intensity, time, etc.