While doing some research on high intensity training (HIT), I sent out a few emails to people who were also interested in this subject and last week was told that Gretchen Reynolds from NY Times was going to have an article in the Sunday Magazine on some research by Dr Barry Braun from UMass. After reading a copy of the article before Sunday, I tried to contact Dr Braun at his office to receive more details from the study so that I could share with all of WHEE. Thus far, I haven't heard back but I did find a few more details.
Join me below for an explanation of why women are at a disadvantage when it comes to losing body fat.
WHEE (Weight, Health, Eating and Exercise) is a community support diary for Kossacks who are currently or planning to start losing, gaining or maintaining their weight through diet and exercise or fitness. Any supportive comments, suggestions or positive distractions are appreciated. If you are working on your weight or fitness, please -- join us! You can also click the WHEE tag to view all diary posts.
Please leave me a comment in the diary to make corrections or additions to the scheduled diary. I noticed that Saturday was left open and normally Edward has a slot here if his work schedule allows. Others?
Scheduled WHEE diaries
April 19
Mon PM - WHEE Open
April 20
Tues AM - WHEE Open
Tues PM - debbieleft
April 21
Weds AM - WHEE Open
Weds PM - Edward Spurlock (Kolata, Ch. 7)
April 22
Thur AM - WHEE Open
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April 23
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Sun AM - louisev Turtle Diary
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April 25
Mon AM - NC Dem
Mon PM - WHEE Open
All the information below in blockquotes is drawn from the Medscape Study online done by Barry Braun and Todd A Hagobian.
First a Definition of Weight Loss
Energy status is defined as the relationship between dietary energy intake (EI) and energy expenditure (EE), typically measured over 24-h periods. Energy status is considered in "balance" when EI = EE, in deficit when EI < EE and in surplus when EI > EE. Energy deficits or surpluses can be incurred by manipulating EI (i.e., underfeeding or overfeeding), EE (i.e., adding or subtracting physical activity) or both
.
Ok, this is just a rewording of our popular terms like "Garbage In = Garbage Out" or "Calories consumed must be less than Calories Expended". You get the picture. We all know this right.
A Few words on Hormones
Those who are really in to losing weight know that hormones like leptin, insulin, and more recently ghrelin (mainly acylated ghrelin) are the key actors as this play unfolds. We have taken a few looks a ghrelin as to how it effects weight loss in a couple of diaries on sleep by
Wee Mama and Brimi.
In these diaries we looked briefly at how sleep effects the production of ghrelin in the stomach and upper intestines. It is ghrelin that is secreted and signals your hypothalmus to begin the signaling of your body that the stomach needs food. It is part of the reason that gastric by-pass surguries have been so popular. When the by-pass is completed, foods no longer go into the lower stomach and upper intestines and move from upper stomach almost directly to lower intestines. Over time, the hormone ghrelin that is normally secreted in the lower stomach almost ceases to function.
Energy-Regulating hormones are commonly classified into two categories, episodic (short-term) and tonic (longer-term) signals.
This is the first time I had seen this classification of the important hormones. Ghrelin is episodic and leptin and insulin are tonic. It sounds simple but it really isn't.
Episodic signals regulate meal initiation and termination and so determine frequency of meals and meal size. Ghrelin, particularly the acylated form that binds to receptors in the hypothalamus, hindbrain, and other tissue, is widely recognized as the main episodic signal to stimulate energy intake.
Tonic signals, such as leptin and insulin, are more likely to regulate overall energy balance and body fat over days or weeks rather than meal to meal. In animals, higher circulating concentrations of these hormones suppress energy intake and stimulate energy expenditure.
We all know that overweight or obese persons normall have more leptin and insulin in their systems which indicates that they must have a "resistance" to these hormones. But leptin and insulin are like the story of the Goldilocks and the three bears and needing to get the porridge "just right". The same holds true for leptin and insulin as studies have shown that too little in the system creates appetite and a reluctance to release body fat after exercise by slowing metabolism.
Women are fighting evolution and must push either a heavier rock up the hill or push it further up the hill.
There! I've said it. Women are at a disadvantage. We know women have higher fat %'s than men. It is all bound up in the plan to procreate and further humans evolution here on earth (and maybe elsewhere). Women have evolved with more fat in the breast area to feed the newborn. During pregnancy they gain additional weight to help feed and sustain the growth and well being of the unborn child. Estrogen plays a huge role in this series as it plays out as well as the appetite cycling the occurs monthly with women. Enough of this for now.
Now let's move to the exercise.
Physical activity, at least in the form of structured exercise, alters hormones that modulate energy balance. A critical issue for interpretation of the exercise data is teasing apart the effects of exercise per se from the potentially confounding influence of an accompanying energy deficit.
So many of us think that exercising increases appetite. It doesn't directly do this. It is the energy deficit that is created by the extra activity that signals the body to produce more ghrelin and also lowers levels of insulin and leptin. It is this reason that exercise is so important to people who are diabetic or pre-diabetic.
The Study?
To directly address the "exercise versus energy status" question in a systematic way, we designed a study to determine whether the effects of exercise on hormonal and appetite responses that regulate energy metabolism were independent of energy status. A second goal of the study was to gain insight into another controversial issue with both basic science and public health relevance — the strong data indicating that, upon the initiation of aerobic exercise training, men lose more body fat than women.
From this study and other readings, you learn that once a sedentary person reaches homestasis and is overweight, the changes in exercises involved must be more intensive than for normal weight persons who exercise regularly. This is true for both men and women.
We observed clear sex differences in the way that exercise altered Energy-Regulating hormones and appetite. In response to exercise without energy added back to the diet, women had higher concentrations of acylated ghrelin and lower concentrations of insulin, both of which would be expected to stimulate energy intake.
For women, even when the energy balance was restored there was still increased ghrelin production. What? This isn't fair.
Acylated ghrelin concentrations did not change in men regardless of energy status. Insulin concentrations were lower in the energy deficit condition, but this effect was completely absent when dietary energy was increased to restore energy balance.
So when men exercise, the level of ghrelin does not change thus there is no immediate (episodic) hormonal increase that directs you to eat more. And as long as the energy deficit stays slightly lower, the insulin also stays lower which helps with more rapid fat loss.
Taken together, these data suggest that exercise induces larger changes to Energy-Regulating hormones in women than in men. The direction of the changes is consistent with the hypothesis that appetite will be stimulated more in women than in men.
It appears that suppressing appetite and thus having a large energy deficit for women violates evolutions monitoring and control over the reproductive health of women. Heck, we know from history and studies that when food shortages occur because of crop failures or climate conditions that women slow conception dramatically. We would like to think it is all by choice but the evidence is that it is also controlled by our bodies and hormones.
In this study, both men and women had their diets controlled after the increased exercising thus the women did not gain back the fat loss from the nergy deficit yet the blood plasma reports showed that women still had increase levels of ghrelin that was promoting hunger. In other sudies where the men and women were allowed to eat ad libitum (in accordance with desire), men did not eat more because their ghrelin levels did not increase while women did increase their food intake in an attempt to return the body to homeostasis.
The key question for me form the study.
Are sex differences in Energy-Regulating hormones and appetite so meaningful that they lead to sex-specific physical activity recommendations?
And this is right where my original research began. I have seen studies that show that for women to lose body fat, the level of exercise and the intensity of activity must be substantial if the women is obese and homeostasis is set. The closer a woman is to normal weight and a lower body fat %, the easier it is to maintain weight by normal walking briskly for 30 minutes 4-5 times each week. For more on this point, I refer you to this study by Laurie Barclay MD at Medscape.
OK, I know that the majority of readership here at WHEE is women so this should create some real questions and hopefully great discussion. I will continue to study this area because I have seen more and more studies that indicate more intensive exercise like HIT programs are needed to blast through the barriers that exist for most. All the studies lend stronger and stronger support for early intervention for weight gain for men and women.
Finally, my research continues to look at the role of estrogen in men as we consume more and more endocrine disrupting chemicals into our water and food supply. Our government needs to act quickly to alert more people to this danger and study how the chemicals in the systems of now pregnant women is causing changes for us to support medically in the next 2-3 generations just as our movement downward on the world economic stage unfolds.
OK, enough despair. My ghrelin levels have risen to such a point that I must take action since i have yet to eat breakfast this morning and decided on purpose to forgo dinner last night since I ate heavily at a late Sunday lunch. Have a great week!