This is an excerpt from a forthcoming book on fat loss, addressing every topic you can think of, from Lyle McDonald. Please visit http://www.bodyrecomposition.com/ for further information on Lyle’s books as well as hundreds of excellent articles.
Women and Fat Loss: An Overview
As a general observation, while men and women show about the same levels of overweight and obesity, women are more likely to be in the extreme obesity category. Far more women are likely to be dieting at any time than men and 80% of the subjects in the National Weight Control Registry are women. While I won’t spend much time talking about it, women are about three times as likely to suffer from various eating disorders such as anorexia nervosa and bulimia (any reader with a true eating disorder must get professional counseling).
Some of this is arguably related to intense societal pressure (and note that the number of men showing up with eating disorders has increased in recent times due to changes in the portrayal of the male physical ideal in popular media) although much of it is biologically based. As always it is the interaction between the two.
For example females are biologically more prone to develop an eating disorder for hormonal reasons (generally the increase in estrogen at puberty) but this is tends to occur primarily in certain types of environments (often involving a lack of control in their overall life). Ultimately, it’s the interaction of the biology and the environment.
In a biological sense, at the risk of depressing female readers at the very start of this, for a variety of reasons that I’ll discuss in some detail, women are basically screwed when it comes to fat loss, at least compared to men. To be honest, in terms of both fat loss and fat gain, women tend to have it worse than men on average and this shows up in nearly every study that either compares men and women or happens to include both.
For example, in original the overfeeding and non-exercise activity thermogenesis (NEAT) study, the four worst responders were women. One of them actually had a decrease in her NEAT during the study (that is while the other subjects were moving around at least somewhat more, she moved around less than normal).
After a meal, while a man will burn some amount of fat, women’s bodies prefer to use carbohydrate and store fat in fat cells, preferentially storing them in lower body fat. When men do store fat it’s more likely to be in visceral fat which is more easily mobilized and burned off. This does have the biological advantage of protecting women from heart attacks, at least until after menopause.
By the same token, when exposed to the same calorie reduced diet, women will always lose less total weight than men and there are a few reasons for this. One is that they are smaller and it’s relatively more difficult for them to create the same deficit (refer back to the math I showed you in the chapter on setting deficits) as a male. As well, men tend to carry more visceral fat which is lost more quickly and easily.
Subcutaneous fat is more difficult to burn off and women, who carry more of it (and especially more lower body fat), will lose at a slower rate for this reason. And while this is ultimately sort of a benefit, since women tend to lose more fat and less LBM than men, their rate of weight loss will be slower due to the loss of fat requiring a larger total deficit than LBM (remember from the chapters on energy balance that losing more LBM will always generate a faster weight loss).
But when this is coupled with a generally smaller deficit, this makes the total rate of weight and fat loss that much slower for women. More fat is being lost which requires a larger total deficit but women generally have a smaller deficit to begin with (1).
When exposed to exercise alone, while men will generally lose some amount of weight and fat, women rarely do when their diet is uncontrolled. In addition to burning less calories than men during exercise (for reasons I’ll discuss), women either increase their food intake or adjust other aspects of their daily activity. So while adding exercise to a man’s day will increase his total energy expenditure, women’s appears not to change. Presumably they reduce NEAT and other activities at other times of the day. Basically, in response to exercise, a woman’s body will compensate.
And that last work basically sums up a woman’s physiological response to diet, exercise, and fat loss: compensation. Yes, men’s bodies clearly fight back but women’s fight back far more on basically every level. Their appetite increases to a greater degree, their metabolisms adjust downwards either more, more quickly or frequently both. That’s on top of the often massive water retention (which I discussed in the section on plateaus and will discuss more later in this chapter) that can mask fat loss for weeks on end.
Then there is the menstrual cycle, the variation in hormones which occurs every month which complicates the entire system. Many aspects of female physiology from appetite, whether they burn carbohydrates or fats more preferentially, energy expenditure, even coordination can change at different parts of the cycle and ignoring this when describing diet or exercise programs can cause a lot of problems (2).
Even there there is enormous variability in a woman’s response to their menstrual cycle with some women seeing profound shifts in everything from appetite to mood to exercise performance and others seeing almost none. Far moreso than men, women are often somewhat unique and delicate flowers.
The menstrual cycle is often disrupted as well with dieting and/or exercise (and especially with the combination). When they are exposed to various stresses both physiological and psychological, the normal menstrual cycle will often shut down partially or completely which causes a host of factors to change (and can cause health problems in the long-term).
Logically this make sense, if she is starving to death (and remember that dieting is just controlled starvation), becoming pregnant is the worst thing she can do. Even there there is huge variability with some women having problems with the most minor of stresses and others having none at all.
About the only time that women have an easier time losing fat is when they are pregnant and/or nursing. During that one time period of their lives, every adaptation to storing and/or mobilizing fat actually reverses itself. Lower bodyfat becomes easier to mobilize and this is clearly to provide energy for breastfeeding. Calories are mobilized from the hips and thighs although, oddly, the triceps often gain fat. Nobody is quite sure why, the best explanation I’ve heard is that it provides cushion to coddle the baby. Maybe.
Which leads to the possible reason that women’s bodies are set up to be this way. Or rather the question “Why do women have it so much harder than men when it comes to fat loss?” It’s been theorized that women, far more so than men, were tasked with the survival of the human race (3). Between carrying children and often being responsible for ensuring their survival, it was that much more crucial for women to be able to handle changes in food supply, increased activity, etc. Women are far more likely to survive a famine than men in the first place and more easily store fat for the future when food becomes available.
Ultimately the entire system is clearly set up to ensure that females would have survived the normal trials and tribulations during our evolution both to carry children to term and to survive long enough for them to survive (4). It was basically all part of ensuring the survival of the human race so make sure to thank your mom. Which, while wonderful, doesn’t help in the modern time when these problems are just a hassle that makes fat loss that much more difficult.
And with that bit of depressing introduction out of the way, I want to do a brief recap of some of the information I have discussed earlier in this book as well as looking at some of the other underlying physiological aspects that make women different in terms of dieting and fat loss.
References
1. Pietrobelli A et. al. Sexual dimorphism in the energy content of weight change. Int J Obes Relat Metab Disord. 2002 Oct;26(10):1339-48.
2. Wu BN1, O’Sullivan AJ Sex differences in energy metabolism need to be considered with lifestyle modifications in humans. J Nutr Metab. 2011;2011:391809
3. Hoyenga KB, Hoyenga KT Gender and energy balance: sex differences in adaptations for feast and famine. Physiol Behav. 1982 Mar;28(3):545-63.
4. Power ML1, Schulkin J. Sex differences in fat storage, fat metabolism, and the health risks from obesity: possible evolutionary origins. Br J Nutr. 2008 May;99(5):931-40.
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