One of the In The News items that Mike put on our homepage got my attention enough to merit a click. The article focused on a newly reported study showing that eating fewer calories will make a rat (and possibly by extension, a human) live longer. On its face, this is a real dog bites man story, since it’s been known for eons that caloric restriction in rats, monkeys, and even in humans will extend lifespan. The news, however, is that instead of the extreme 40% reduction of calories many of the early trials adopted–a Spartan regimen that makes even rats and monkeys depressed–the reduction of this study was modest. Reducing the rats’ intake by only 8% of total calories increased their longevity.
What’s not mentioned in this paper, or for that matter in most reports of caloric restriction and longevity, is that because of the basic structure of lab animals’ diets, the lion’s share of the calorie cutting comes from cutting their carbs. Protein in their chow has to stay about the same, fat is already pretty low, and so the big chunk of any reduced calorie lab protocol comes from restricting carbs.
That’s what makes this study so important to you and me. If indeed, cutting a mere 8% of calories per day can improve health and extend life, we’re in luck; most of us are already there. Like the rats, we’ve carved our reduction out of the carb category. The trick is not to replace all of it with something else.
In the standard 2000 calorie diet, an 8% reduction would amount to cutting out a mere 160 calories a day. Done as carb, this would amount to only 40 grams a day. If Americans would adopt even a modest lower carb diet–say 60 or so effective grams a day or even a maintenance level of 80 to 100 grams–it would cut a couple of hundred grams of carb out of their diets as quick as a lab rat can flick its tail. A couple hundred grams of carb at 4 calories per gram would result in a calorie savings of 800 calories. They could replace some of them with protein, some with good fats, and as long as they don’t replace all of them–keeping that magic reduction of 160 to 200 calories a day– they’ll not only sensibly lose weight, but they’ll live longer to enjoy it.
Sounds like a win-win to me.
For the rest of us low-carb veterans, who already restrict our carbs to keep our insulin, blood sugar, lipids, and inflammatory markers in line, but may have let our calorie intake float up to a maintenance number, all it will take is a very modest reduction in good fat intake–at 9 calories a gram, we can get there by giving up a tablespoon and a half of oil, butter, or cream a day.
If the study’s hypothesis proves valid in humans–and I grant that at this stage, that’s a pretty big if–it seems to me that such a modest reduction in intake is not much of a sacrifice to make toward furthering our healthy existence by enough years to see the grandkids grow up to have kids of their own.
I’m on it!
Thank you for raising this subject – I’ve seen a couple of hints that carb restriction could work in a similar way. A short New Scientist report on 16th May 2006 (http://www.newscientist.com/channel/health/mg19025515.600.html)finished with:
“The actions of growth hormone are somehow implicated in linking caloric restriction to longer life,” Bartke says. Insulin may be the connection. Both groups of long-lived mice had a greater sensitivity to insulin, and caloric restriction in the mutant mice failed to increase their strong insulin sensitivity any further.
And an interview in October 2003, with a scientist working in this field (Cynthia Kenyon) had this interesting bit:
http://www.newscientist.com/article/mg18024175.300.html
(sorry if it’s only available to subscribers)
But for now, caloric restriction seems the one proven way to extend lifespan. Is that why you’ve virtually given up carbohydrates?
That’s not necessarily why I do it. I do it because it makes me feel great and keeps me slender. And I don’t feel really tired after a meal. But I think if I wanted to eat in a way that extended lifespan this is how I would do it. In fact, I stopped eating carbohydrates the day we found that putting sugar on the worms’ food shortened their lifespans.
How does it work?
I eat a diet that keeps my insulin levels low. So, for example, at breakfast I have bacon and eggs with tomatoes and avocados. It’s bit like the Atkins diet. I don’t actually know if I eat fewer calories, but I feel great and I weigh what I did in high school. I certainly wouldn’t want to be hungry all the time, but I’m not, I’m never hungry. I tried caloric restriction just for two days but I couldn’t stand it, being hungry all the time.
“Insulin resistance is a risk factor for just about any problem you don’t want to get: diabetes, atherosclerosis, cancer. It’s sort of intuitive that the opposite situation would be beneficial.”
She then went on to explain what great things eating LC had done for her blood profile, and that LCers do eat veggies (shame nobody was listening!).
COMMENT from MD EADES: Yes, it is a shame that so often nobody is listening when something positive about a lower carb regimen gets said.
I think almost everybody (myself included) adopts a low carb diet initially either to stay lean, lose weight, correct lab values, or feel better. That’s certainly why we’ve stuck to one for over twenty years. It’s just a happy side benefit that it may also extend productive and healthy lifespan.
And you’re correct that the connection is probably through lowered insulin. Studies on healthy human centenarians have repeatedly shown that they have three things in common: relatively low blood sugar, low insulin, and low triglycerides. And all it takes is a low carb diet to do that, so maybe we really are already there.