March 16, 2006
Weight Training Exercise Reduces Middle Age Fat Bulge

Pump iron to keep off the fat.

(Phoenix, AR) - Women who lift weights twice a week can prevent or at least slow down "middle-age spread" and weight gain, a University of Pennsylvania School of Medicine researcher reported today at the American Heart Association's 46th Annual Conference on Cardiovascular Disease Epidemiology and Prevention.

A study of 164 overweight and obese (body mass index of 25-35) women between 24 and 44 years of age, found that strength training with weights dramatically reduced the increase in abdominal fat in pre-menopausal participants compared to similar women who merely received advice about exercise.

"On average, women in the middle years of their lives gain one to two pounds a year and most of this is assumed to be fat," said lead author Kathryn H. Schmitz, PhD., Assistant Professor, Center for Clinical Epidemiology and Biostatistics. "This study shows that strength training can prevent increases in body fat percentage and attenuate increases in the fat depot - or 'belly fat' - most closely associated with heart disease. While an annual weight gain of one to two points doesn't sound like much, over 10 to 20 years, the gain is significant."

Women in the two-year weight-training program decreased their body fat percentage by 3.7 percent, while body fact percentage remained stable in the controls. The strength-training reduced intra-abdominal fat, which is more closely associated with heart disease and metabolic disturbances. More specifically, the women who did strength-training experienced only a 7 percent increase in intra-abdominal fat compared to a 21 percent increase in intra-abdominal fat among controls.

The study - dubbed The SHE study, for The Strong, Healthy, and Empowered - examined whether twice-weekly strength-training would prevent increases in intra-abdominal and totally body fat in women who were overweight or obese. The women initially were separated by baseline percentage body had booster session four times yearly with certified fitness professionals over two years. The control fat and age. The strength-training group participated in supervised strengthening classes for 16 weeks, and group received a brochure recommending 30 minutes to an hour of exercise most. days of the week. All of the women were asked not to change their diets in ways that might lead to weight changes while they were participating in the study.

The weight-training sessions took about an hour, and the women were encouraged to steadily increase the amount of weight they lifted. The weight training included exercises for all major muscle groups, including the chest, upper back, lower back, shoulders, arms, buttocks and thighs. The maximal amount of weight women could lift once - called a one-repetition maximum test - increased by an average of 7 percent in bench pressing and 13 percent in leg press exercises.

Researchers measured the participants' body composition with a dual energy X-ray absorptiometry (DEXA) scan and measurements of abdominal and total body fat by single slice CT scan at baseline, and again at one and two years.

Why does weight training have this effect? Does it act only by the increase in calories burned during the exercise? Or does the resulting increase in body muscle mass cause an on-going higher rate of calorie burn that is not offset by higher appetite? Or does the exercise release endorphins or other compounds that decrease appetite? Or some combination of the above?

To put it another way: Why doesn't appetite regulation by the brain prevent weight gain as people age? Was the weight gain selected for to prevent starvation in our ancestors? Or is it a side effect of reduced ability to regulate bodily functions due to brain aging or signalling systems aging elsewhere in the body?

Share |      Randall Parker, 2006 March 16 03:25 AM  Brain Appetite


Comments
odograph said at March 16, 2006 6:30 AM:

I'm sure you've seen the papers on the hunter-gatherer energy balance. Here's a good short one, called “An evolutionary perspective on human physical activity: implications for health” (link to the pdf)

My two comments on the above would be (1) we see life expectancies for pre-agricultural communities quoted at 20-some years, and (2) we are living far outside the "normal human range" for diet and exercise. So why would there be evolutionary pressure for an "old body" (such as my 40-something male one) to maintain fitness through inactivity?

I think a common theme among the "paleo" diet and exercise folks is that we have a natural laziness, and an inclination not to waste our energy or our muscles, but that pre-agricultural life forced us to get moving. Now, our labor saving devices are so good that many of us can live truly lazy lives.

curious george said at March 16, 2006 7:38 AM:

Weight training has also been found to reduce osteoporosis in women later in life! So come on ladies...let's hit the gym!

Sumyung Guy said at March 16, 2006 7:46 AM:

I'm glad that they're doing studies to confirm this, but really this has been known about for some time. Regular cardio and weight training exercise in moderate amounts, maintained over one's lifespan, is the equivalent of a "wonder drug" for reducing health problems and increasing overall health. It's just a lot more work than popping a pill.

That's the main reason that people don't do it, or if they start they don't maintain it...it's work. I should know, I really should spend more time in the gym myself but I'm a lazy-ass. Time for me to get off my butt at lunch today and head over there :-)

PacRim Jim said at March 16, 2006 9:41 AM:

There's a simpler explanation for weight gain in middle age. For 99%+ of our history, humans only lived about 25 years, long enough to bear children in their teens and raise them to their teens, at least by one parent. As futile as it sounds, we live to reproduce. After that, we are more than superfluous, we use up precious resources needed by the young to reproduce. True, in the last few centuries we have developed the ability to provide abundant resources for all, but our genes don't know that. They know scarcity and the reproductive imperative. Genetic engineers will have to re-engineer our genes to conform to the modern environment. Can hardly wait.

Ryan said at March 16, 2006 9:50 AM:

I guessing here, but weight training and the resulting increase in muscle mass probably has very positive effects on insulin in the bloodstream. I would think that the more muscle mass you have, the calories you burn just existing, the quicker the carbs (primary fuel source) gets used up. So the body might be closer to a ketonic state which burns fat instead of carbs as it's main energy source.

Doug said at March 16, 2006 12:08 PM:

Randall, Arthur De Vany considers your questions and similar ones relating diet and exercise to health and fitness on his weblog. His views and supporting arguments are interesting and persuasive, especially since he's in his late sixties, but seems to have the health of a vigorous thirty-year-old.

momochan said at March 16, 2006 2:07 PM:

Regarding the >30 year life expectancy for early humans -- I thought that a hunter-gatherer who survived childhood had a fair chance of reaching 50; it was infant/youth mortality that drove down the average lifespan. Can anyone give any details? Of early *adult* skeletons found, what is the mean, median, and range of age of death? thanks

Bob Badour said at March 16, 2006 4:08 PM:

Randall,

I find some of your questions misquided. As people age, gastric motility slows and appetite decreases. However, these two phenomena at least partially cancel each other out.

At the same time, as we age anabolic hormone levels decrease (testosterone for instance) causing a loss of muscle mass. The loss of muscle mass results in a reduced basal metabolic rate with the subsequent increase in stored fat. Resistance training counters and even reverses the muscle atrophy keeping the basal metabolic rate high.

You seem too focussed on appetite to me. Appetite itself is a function of nutrition and exercise. It seem much better to me to focus on nutrition and insulin response.

odograph said at March 16, 2006 4:25 PM:

Lifespans ... I think the idea is that there have generally been "old people" throughout history, but there were fewer of them, leading to the statistical shortness of life expectancy.

We have many drives (concern for adult children, re-commitment to grandchildren) that would have an evolutionary benefit even after we stop breeding. I think that is well covered even in the popular literature. YOU at age 60 will (probably) not have more children, but a propensity to care for your grandchildren increases the odds of your genes surviving.

... I'll leave it to the serious researchers to guess how active those paleo-grandparents were in assorted cultures.

hamerhokie said at March 18, 2006 10:44 AM:

It's widely understood by those in the fitness world that increasing muscle mass increases at-rest metabolic rate and thus burns more calories over time. This study just verifies what millions have known for years.

Brett Bellmore said at March 19, 2006 7:55 AM:

I notice the age group cuts off right about the point where you stop producing appreciable growth hormone, which is necessary to gain muscle mass from such exercise. Fortunately hormone suplimentation is available now to change that, unfortunately, the price is remaining unreasonably high.

A point I wonder about is the feasiblity of somebody in their late 40's, such as me, doing growth hormone suplimentation *cycling*, with a month of suplimentation and intensive exercise, alternated with a couple months of no suplimentation and coasting to avoid the muscle damage the exercise causes if you don't have the hormones in your system. THAT I could probably afford.

Randall Parker said at March 19, 2006 9:53 PM:

Bob,

I understand that muscle mass decreases with age. But I do not think that fact by itself answers the questions I asked. We could have suffered decrease muscle mass without an increase in fat. Some people experience that pattern of change.

Appetite: I focus on it because it the purpose of appetite regulation is to control quantity of food consumed. Why does appetite not decrease when the number of calories burned goes down? Why doesn't the brain and endocrine system regulate the appetite based on percent body fat?

Brett Bellmore said at March 20, 2006 4:05 AM:

Because during most of our evolutionary history, the consequences of being overweight were far less than the consequences of being underweight, so our regulatory systems are primed to err in the safe direction? It must be remembered that modern society, with both an abundance of food, and little need for constant physical labor to obtain it, bears little resemblance to the conditions present during most of our evolutionary history, so it's scarcely suprising we're ill adapted to it.

rob said at March 20, 2006 6:36 AM:

Randall, I'm surprised you didn't comment on the NYT magazine article about "choice moms."

Bob Badour said at March 20, 2006 8:03 AM:
Why does appetite not decrease when the number of calories burned goes down?

Randall, if you are talking about the decrease in calories burned due to the decreased metabolic rate due to aging, I would point out that appetite does go down. However, at the same time, gastric motility slows and we extract more calories from the food we eat.

Why not focus on increasing gastric motility to youthful levels?

Keep in mind, too, that the decrease in muscle mass is an invention of modern convenience. Our forebears had to haul water and cut wood even in old age. My Aunt Gin, until a few years ago, lived in a small cottage with no electricity or running water. She split the wood for her stove. In the summer, her shallow dug well would go dry, and she would carry two 5 gallon cannisters of water from her brother's house about 300 meters away. She was a small woman so 90 lbs of water is pretty much her own body weight, and she carried that daily for 300 meters without pausing to rest well into her 80's.


Why doesn't the brain and endocrine system regulate the appetite based on percent body fat?

The answer to that is obvious: In evolutionary terms, we never had any need to. The brain and endocrine system regulate appetite based on the availability of food.

Randall Parker said at March 20, 2006 5:35 PM:

Rob,

Choice moms: I've spent my time last couple of days fighting spam and dealing with blog configuration. My comments went away due to another database index corruption due to spam attacks. I'm putting in new anti-spam defenses. Hence my lack of time to actually write blog posts. I've got more changes coming this week that'll make spam attacks a whole lot harder.

Anyway, I'll look for the Choice Moms article.

Bob,

You are missing the point that many people stay skinny in their 20s and 30s. They too have lots of food available. So why start gaining weight only starting in their 40s?

Bob Badour said at March 21, 2006 4:47 AM:

Randall,

What makes you think increasing gastric mobility to youthful levels will fail to keep those who are skinny in their 20's and 30's skinny later in life?

They start gaining weight in their 40's because they lose muscle mass due to the relatively easy modern life. I thought that seemed clear enough in what I posted.

Rockstarbabu said at October 1, 2009 11:14 PM:

hi every body I'd just like to say, you can totally do it! I have a
friend who was overweight... she would never tell me exactly
how much she weighed because she was embarrassed, but it was
over 200 pounds. At that time, I weighed around 155, but over
the next 8 months, I lost 20 pounds.

As she saw me losing weight, just by not eating as much junk
food and exercising twice a week, she realized that she could
also lose weight. She started to make an effort and also began
to lose weight.

A year after I started losing weight, everyone began to comment
on how terrific she looked. Although she still hadn't reached her
eventual target weight, she weighed around 150, which was such an
achievement that she looked so self-confident to everyone else,
which only further motivated her.

We would motivate each other, go to the gym together, and just talk
about it. Having a friend who has the same goals as you can really
help to motivate you.

We both found that if we went to the gym regularly (at least twice
a week) we were also more likely to eat healthily, because we didn't
want to ruin all of our hard work! Also, try not to be discouraged if
exercising is hard at first. It will be, for awhile, until your body
adjusts. Exercising for 20 minutes at a slow pace is better than not
exercising at all.thanks for share it .

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