Tag Archive for: caloric restriction

How Calorie Restriction Affects Your Metabolism

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Resting metabolic rate (RMR) is the number of calories you use while at rest—just lying around doing nothing. It’s the calories your body uses to operate your internal organs and your brain, etc. From the second you open your eyes, the calories you burn are considered activity-related calories.

The concern in trying to restrict calories as in the CALERIE Study is how that will affect RMR. Will it be proportional or will RMR go down too much, leaving you feeling too tired to do anything?

Researchers examined the data in a subset of normal-weight subjects over a year, looking at tissue losses and metabolic adaptations that contributed to the reduction in RMR. In other words, which organs or systems were impacted the most to lower RMR? They calculated the differences before and after the secondary study to see what changed, and found that the RMR was reduced by only 101 calories per day.

There’s more to come from the CALERIE study. One thing for sure is that a small reduction of 12% to 15% in calories every day can do you a whole lot of good—no special diets necessary—without losing your get up and go.

What are you prepared to do today?

        Dr. Chet

Reference: Int J Obes (Lond). 2022 Feb 18. doi: 10.1038/s41366-022-01090-7.

Can Cutting Calories Improve Your Mood?

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In research like the CALERIE study, there’s a tendency to focus on physical changes but what about mood, depression, and quality of life (QOL)? Did researchers find changes in those variables as well? Let’s take a look. While the two-year span of the data analyzed varied slightly from other phases of the study, physiological results were virtually identical to the other phases I’ve talked about in previous Memos.

Testing Procedures

For those readers familiar with the assessment tools typically used in measuring psychological variables, here’s a list of the instruments they used.

Mood: Beck Depression Inventory-II [BDI-II] and the Profile of Mood States [POMS]

QOL: Rand 36-Item Short Form and Perceived Stress Scale

Sleep: Pittsburgh Sleep Quality Index [PSQI]

Sexual function: Derogatis Interview for Sexual Function Self-report

Results

For simplicity’s sake, I won’t use numbers to report the results, because unless one is familiar with the scale for each assessment it wouldn’t be meaningful. Every following relationship was statistically significant or correlated. Compared with the ad libitum (AL) group, the caloric restriction (CR) group had significantly improved mood, reduced tension, and improved general health and sexual drive at month 24. Sleep duration had improved by month 12 and was sustained through month 24.

Greater percent weight loss in the CR group at month 24 was associated with increased vigor and less mood disturbance, improved general health, and better sleep quality. The researchers concluded that there was no negative impact of CR on psychological variables in normal-weight people.

I have a tendency to put more faith in measurable variables such as blood pressure or heart rate than inventories and questionnaires, but the results demonstrated that all measures moved in a positive direction when restricting calories: better perception of mood, health, QOL, more and better sleep, and even sexual vigor. There are indications that CR may be beneficial even in people who are normal weight.

What are you prepared to do today?

        Dr. Chet

Reference: JAMA Intern Med. 2016 Jun 1;176(6):743-52.

Saving Muscle While You Reduce Calories

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Several studies have been published from the CALERIE study data with even more interesting revelations, so I’ll review several over the next few Memos. I’ll start with changes in body composition in those who restricted calories (143 subjects) and those who continued to eat normally (75 subjects), often called ad lib or ad libitum. Remember, the purpose of the study was to achieve a 25% reduction in calorie intake and sustain it for two years in subjects who began at normal BMI.

The caloric restriction (CR) group achieved only an 11.9% decrease in CR over two years but still showed significant changes:

  • 16.7 pounds decrease in weight compared with a one pound gain in the ad libitum (AL) group
  • A decrease in waist circumference of 2.4 inches versus a 0.5 inch increase
  • Fat mass decrease of 11.9 pounds compared with a 1.1 pound gain
  • A 4.4 lb. decrease in fat-free mass compared with no change at 24 months
  • Although the CR subjects lost some fat-free mass, the loss of fat exceeded the expected proportional loss found in the typical weight loss program of 50% fat mass and 50% fat-free mass

That’s the surprising result: the study showed that a moderate reduction in calories did not abnormally impact the proportion of muscle loss to fat loss: fat loss exceeded muscle loss. Rather than protein intake, the calories used in activity contributed to sustaining muscle mass—exercise helped maintain muscle.

We’ll examine another paper from the CALERIE Study on Saturday.

What are you prepared to do today?

        Dr. Chet

Reference: Am J Clin Nutr 2017;105:913–27.

It’s All About the Calories!

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One of my long-held beliefs is that where weight is concerned, it’s all about the calories—and I’m happy to say that this study reinforces my belief.

But when I’m wrong, I’ll tell you. Case in point: as I continued to examine the CALERIE trial, it became apparent I had made a mistake in the number of subjects and the percentage of caloric restriction. One paper reported 11% caloric restriction over two years, another 15.9%, and a third 14.1%; I referred to that one in Tuesday’s Memo on caloric restriction and immunity. This was a five-year data collection study that began in 2007 and finished in 2012. Different papers covered different time periods, and the data set used was appropriate for the time period examined; there were additions and dropouts until two years before study ended in 2012.

The Purpose of the Study

The primary purpose of the study was to develop a program that would help people maintain a 25% decrease in calories by using technology and a continuous support system. They also had a variety of physiological, psychological, and genetic factors to examine. That’s why data from 15 years ago are still being examined today.

There is one more thing we need to know. This was not a weight loss program; all the subjects were normal weight. They wanted to find the level of caloric restriction that would provide benefits but not cause problems with the immune system, such as the rodent studies found at 40% caloric restriction.

I think they succeeded; 25% caloric restriction was too much in free-living people, but 10% to 15% caloric restriction was doable with no issues in body composition, psychological factors, or several other variables they have reported on such as the decrease in an enzyme that sabotages the immune system as in Tuesday’s Memo.

It’s About the Calories

There were no special diet plans recommended. Subjects were provided support on how to reduce calories along with strategies to use if their interest started to wane over the entire two years. One of the researchers commented when interviewed that perhaps there will be a more effective diet between Mediterranean, keto, or some other way of eating.

No, there won’t.

I’m more convinced than ever: it’s all about the calories. I think people should choose to eat the healthiest foods they can afford so they get the optimal types of fat, phytonutrients, and other factors. But it was, it is, and it will always be about the calories—for weight loss if you’re overweight, for improved health if you’re normal weight, or both.

What are you prepared to do today?

        Dr. Chet

Reference: SCIENCE. Feb 2022. 375(6581):671-677