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Diet Alone Will Not Likely Lead to Significant Weight Loss.

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Research Demonstrates Diet Alone Will Not Likely Lead to Significant Weight Loss.

Newly-published research by scientists at Oregon Health & Science University demonstrates that simply reducing caloric intake is not enough to promote significant weight loss. This appears to be due to a natural compensatory mechanism that reduces a person’s physical activity in response to a reduction in calories. The research is published in the April edition of the American Journal of Physiology – Regulatory, Integrative and Comparative Physiology.

“In the midst of America’s obesity epidemic, physicians frequently advise their patients to reduce the number of calories they are consuming on a daily basis. This research shows that simply dieting will not likely cause substantial weight loss. Instead, diet and exercise must be combined to achieve this goal,” explained Judy Cameron Ph.D., a senior scientist at OHSU’s Oregon National Primate Research Center, and a professor of behavioral neuroscience and obstetrics & gynecology in the OHSU School of Medicine, as well as a professor of psychiatry at the University of Pittsburgh.

To conduct the research, Cameron and OHSU post-doctoral fellow Elinor Sullivan, Ph.D., studied 18 female rhesus macaque monkeys at the Oregon National Primate Research Center. The monkeys were placed on a high-fat diet for several years. They were then returned to a lower-fat diet (standard monkey food) with a 30 percent reduction in calories. For a one-month period, the monkeys’ weight and activity levels were closely tracked. Activity was tracked through the use of an activity monitor worn on a collar.

“Surprisingly, there was no significant weight loss at the end of the month,” explained Sullivan. “However, there was a significant change in the activity levels for these monkeys. Naturally occurring levels of physical activity for the animals began to diminish soon after the reduced-calorie diet began. When caloric intake was further reduced in a second month, physical activity in the monkeys diminished even further.”

A comparison group of three monkeys was fed a normal monkey diet and was trained to exercise for one hour daily on a treadmill. This comparison group did lose weight.

“This study demonstrates that there is a natural body mechanism which conserves energy in response to a reduction in calories. Food is not always plentiful for humans and animals and the body seems to have developed a strategy for responding to these fluctuations,” added Cameron. “These findings will assist medical professionals in advising their patients. It may also impact the development of community interventions to battle the childhood obesity epidemic and lead to programs that emphasize both diet and exercise.”

http://www.ohsu.edu/xd/about/news_ev...arch-demon.cfm

Very cool.

Jack LaLane made his living telling people that weight loss required physical activity.

only with exercise?

Then how does one explain the "6 week body makeover" of Michael Thurmon which includes very little exercise or the results of Atkins or Atkins-type, locarb weight loss programs?

I myself lost over forty pounds over a six month period, a full year ago. I quit my usual light dumbbell/resistance bands exercise in favor of yoga, especially the deep breathing exercises, during the losing period.

I'm back to regular, light exercise (I'm sixty six, five ten and one seventy five) and haven't gained or lost more than one or two pounds since losing the original forty pounds. I certainly don't have a six-pack, and although not entirely flat, I certainly don't carry any visible paunch.

I think sometimes diet is enough. Just my take on the subject.

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Originally Posted by Nero Germano (Post 74532)

Most of the initial rapid weight loss on Atkins or Atkins type diets is just glycogen and water. Subsequent weight loss will largely depend on whether you keep up with your normal daily activities, which most of us have no choice over, or whether you decide to just sit on your ass all day because you don't have the energy to do anything. My guess is the monkeys did the latter.

Very interesting, and I think pretty intuitive. Gary Taubes talks about this when he preaches that Cals In and Cals Out are not independent variables. From my own personal experience, and I'm sure anyone that has dieted can corroborate this, when cals in are low, so is general energy level.

Darryl et al, any data on how resting calorie usage changes depending on the number of surplus calories available? I've observed that during hypocaloric periods, my resting body temp, sleep cycle, and other thigns drastically differ. I would also venture a guess that I have more "nervous energy" usage when relatively well-fed (tapping my foot, drumming my fingers, etc.).

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Originally Posted by Nero Germano (Post 74532)

What you described is the concept of individual variability.

The purpose of research studies is to see whether or not the results produced are significantly large enough to disprove the possible sampling error from inherent individual variability. I haven't seen the statistics on this study, so I don't know if they are legit, but I assume that if it's a peer reviewed study, the statistics are trustworthy.

The better criticism of the paper is that it was done on monkeys. Yes they are good representations of humans and I find the insights of the study to be good. Normally at the end of these studies, the researchers themselves say that human testing is necessary. They don't say, "well my friend billy joe lost weight eating cheese and apples, so we think our results might be wrong."

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Originally Posted by Brian Stone (Post 74547)

Darryl et al, any data on how resting calorie usage changes depending on the number of surplus calories available? I've observed that during hypocaloric periods, my resting body temp, sleep cycle, and other thigns drastically differ. I would also venture a guess that I have more "nervous energy" usage when relatively well-fed (tapping my foot, drumming my fingers, etc.).

Normally I'd be able to give you some numbers on this but nearly all my books are in storage at the moment.

Anyway, as a general rule your body is relatively insensitive to small changes in daily energy intake so you won't notice any difference with variations of +/- 5% of total calories. If there is a large decrease in energy intake then your body will attempt to reduce energy output to match intake as demonstrated by this study. How your body reacts to a hypercaloric diet will depend to a great degree on it's macronutrient content; a high-carb hypercaloric diet will result in a increase in spontaneous physical activity but a high-fat hypercaloric diet won't.

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If there is a large decrease in energy intake then your body will attempt to reduce energy output to match intake as demonstrated by this study.

I guess the difference between us and monkeys is that people can push through their body trying to reduce energy output...

Why are we still funding studies about stuff people knew 50+ years ago to be true?