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basmwklz OP t1_ivadwry wrote

Abstract: >Chronic calorie restriction (CR) results in lengthened lifespan and reduced disease risk. Many previous studies have implemented 30–40% calorie restriction to investigate these benefits. The goal of our study was to investigate the effects of calorie restriction, beginning at 4 months of age, on metabolic and physical changes induced by aging. Male C57BL/6NCrl calorie restricted and ad libitum fed control mice were obtained from the National Institute on Aging (NIA) and studied at 10, 18, 26, and 28 months of age to better understand the metabolic changes that occur in response to CR in middle age and advanced age. Food intake was measured in ad libitum fed controls to assess the true degree of CR (15%) in these mice. We found that 15% CR decreased body mass and liver triglyceride content, improved oral glucose clearance, and increased all limb grip strength in 10- and 18-month-old mice. Glucose clearance in ad libitum fed 26- and 28-month-old mice is enhanced relative to younger mice but was not further improved by CR. CR decreased basal insulin concentrations in all age groups and improved insulin sensitivity and rotarod time to fall in 28-month-old mice. The results of our study demonstrate that even a modest reduction (15%) in caloric intake may improve metabolic and physical health. Thus, moderate calorie restriction may be a dietary intervention to promote healthy aging with improved likelihood for adherence in human populations.

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arkteris13 t1_ivauuwp wrote

The main issue here is that very few humans have an ad libitum diet. It could just mean our animal housing practices are detrimental to their health.

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DanOMight_801 t1_ivaxt6i wrote

I would describe many Americans as having an ad libitum diet. I agree with your rationale about drawing conclusions, there are always plenty of factors. In this case we have no reason to expect different housing practices for each population, so it’s reasonable to minimize that as a cause for observed differences. The study suggests this is a potential phenomenon that could apply to humans, but invites further investigations based on objective scientific observation.

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kvotebloodless t1_ivboddv wrote

In the biology of aging course we talked about this too. You could assume by giving mice access to food 24h a day, they will eventually just be over fed. And by limiting the diet to a healthy amount, their life will be naturally elongated. So the calory restriction theory is not as proven as many say.

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triffid_boy t1_ivceurb wrote

These aren't the only studies that suggest a benefit to CR, and the mechanism - via mTOR - is reasonable.

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Elphya t1_ivdokya wrote

"You could assume by giving mice access to food 24h a day, they will eventually just be over fed."

Anyone that works with mice in animal facilities knows that's not true.

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uninstallIE t1_ivdq1gn wrote

>very few humans have an ad libitum diet.

How do you mean this? Globally, inclusive of global poverty and food access?

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arkteris13 t1_ivdq7i4 wrote

We typically eat to satiation, rather than consume constantly. In terms of lab animals, you see the former in rats, but mice will constantly nibble at their chow.

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uninstallIE t1_ivdqvyd wrote

Most people do not stop eating at satiation. They eat beyond this, and often very much so. However, eating whenever you want and stopping when you are satiated is still ad libitum.

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TheMailmanic t1_ivbcspp wrote

What does 15% cr mean exactly? Is that 15% relative to ad libitum? Or 15% relative to maintenance calories?

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r0botdevil t1_ivbs5um wrote

That's what I'm wondering as well, but it has to be the former as the latter would invariably result in death by starvation over the long term.

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TheMailmanic t1_ivbsqld wrote

Yeah agreed the calorie intake must be at maintenance or above to avoid starving and losing weight continuously.

In terms of applications to humans, it seems like maintaining weight at a low-ish body fat % with resistance training to maintain lean mass results in the best health outcomes generally. Calorie intake has to be adjusted depending on whether you’re trying to lose/maintain/gain

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Okay_Try_Again t1_ivdpxmu wrote

You don't keep losing weight if you sustain a calorie deficit, your metabolism adjusts to match what you take in, among other factors. That is why 95% of people who restrict calories or increase exercise to lose weight regain within 3-5 yrs even when they keep it up, in reality 2/3 of dieters end up at a heavier weight than they started after 3-5 yrs.

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TheMailmanic t1_ivdq8yo wrote

Well yes your bmr goes down as you lose weight Because it’s a function of your body weight to some extent

That said, a calorie deficit is the only real way a person will lose weight over time. The people who rebound are the ones who do extreme diets that they can’t sustain long term. Plenty of people have done slow and steady calorie deficits to reach a target weight then raise calorie to maintenance to maintain that weight

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Okay_Try_Again t1_ivg1dbo wrote

Not just your bmr goes down, hunger hormones increase as well.

Look at the research you will see that all the studies here a large amount of people can keep off the weight are just one yr long. When you get to a 3-5 yr study, the numbers for people who can maintain the loss are 5-20 percent. And if you have obesity when you try to lose weight the odds go way down, because obesity changes your hormones even further.

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Concavegoesconvex t1_ive10gj wrote

The problem is that dieters go back to the diet that got them overweight in the first place. Also my personal theory is that people starve-diet themselves, losing muscle in the process, which will indeed lead to less calories burned.

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