While estimating BF% is important for many reasons, at least one of those is for you to determine what dieting category you are in. This is a delineation Lyle Mcdonald has used for many years and is based around the fact that a woman's physiology is changing to one degree or another based on her current BF%. I won't detail those here but those physiological changes impact on many practical aspects such as how much protein she might need while dieting, her relative risk of menstrual cycle dysfunction, how rapidly she will be able to lose weight or fat, her relative risk of muscle loss and others. When we look at the research relating to women's body fat issues, it will be important to recognise what category the subjects being studied are in. I've presented the categorisation system using the BF% methods outlined in the last blog.
While I have presented the table with rather discrete cut off points, please realise that this is a continuum. The cutoff points are based on underlying physiology but it's not as if physiology changes completely from one category to the next. A woman at 35% body fat is far closer to a Category 2 female physiologically than a woman at 45%. Similarly, a Category 2 dieter at 25% is essentially the same as a Category 1 dieter. But some sort of delineation is required to make the system work and I'll only suggest that women at the very low end of one Category should consider themselves in the next lower category in terms of the rest of this blog. So a woman at 35% body fat should consider herself in Category 2 in terms of her diet set up, etc.
Some Category Comments
Before looking at some last practical issues, I want to make some brief comments about the Categories above and who might typically be found within them. In general, the Category 1 female tend to be involved in some degree of training. They could be in one of the physique sports, a performance sport or be what I will call a serious trainee (possibly workout out intensely 5-6 times per week but not competing). In many cases, either for performance, competition or appearance, these women will want to lose some amount of body fat As frequently they may want to gain muscle. The physique athlete may wish to bring up weak body parts and many performance sports benefit from increased muscle mass. I'd note that there can be a Category 1 female who is not active or training. They frequently are genetically lean although they still want to lose weight. Weight gain is a rare but very occasional goal.
Category 2 tends to span the broadest range of possible situations since it matches up with relatively average BF% for women to begin with. Athletes may be in this group as many sports do not require extreme leanness, many recreationally exercising women may also be in this group. It's possible for a physique athlete who let their body fat get away from them in the off-season to be here although that can cause a lot of problems when it's time to diet down for a contest. The serious trainee might fall here if here diet isn't set up correctly such that, despite all of the training, she is not losing body fat or maintaining a lower body fat effectively . It's just as likely for women to be in Category 2 who are sedentary or only minimally active. Fat loss is likely to be the primary goal in this group.
In general, Category 3 women are the least likely to be involved in any sort of training program or sports although there are certainly exceptions. Overall, it is far more likely for the Category 3 women to be relatively sedentary. In this case, fat/weight loss and/or improving health and fertility is likely to be the exclusive goal.
A Female Specific Issue for Tracking Body Composition
With the understanding of what body composition/BF% is and how to measure and track it, I want to address a female specific issue that goes unconsidered by most that the normally cycling woman must contend with (women with a hormonal modifier have less of an issue with this). That issue is the often considerable changes that occur throughout the menstrual cycle in water retention. This not only impacts on scale weight but can also impact on other methods of tracking.
Both calipers and the tape measure measurements can readily be altered during different weeks of the month and, depending on its degree, water retention can make women feel or look puffy in the mirror or in pictures or make clothing fit differently. As I described in later blogs, the late follicular and late luteal phase (Weeks 2 and 4 respectively) tend to be the worst in this regards with the early follicular (Week 1) generally showing the lowest body weight and early luteal (Week 3) being somewhere in-between.
This causes several problems. The first is that it can exacerbate the normal issues many have with the scale. The woman who is already fixated on the small day-to-day changes can be driven mad by the weekly changes as she will be adhering to her diet and exercise program and almost over night, her weight spikes by several pounds or kilograms. Hopefully ny now you will avoid at least this issue now that I have pointed out what those types of fluctuations mean but I've even known female trainees who, despite knowing full well the difference between body composition and body weight, still getting affected by these types of weight shifts. Even taking a rolling average as I recommended above doesn't eliminate this because the average value and trend line will be shifting up and down each week.
Within any given week, the rolling average will be useful but from week to week it will not be. An added issue is that it makes tracking changes more difficult for the normally cycling woman compared to women with most of the hormonal modifiers or men since comparing different weeks of the cycle to one another won't give any accurate indication of what is happening in response to her diet or exercise program.
To better illustrate this, I've shown a hypothetical month of average weekly body weights and how they might change in different weeks of the cycle along with month to month. These numbers are for illustration only and any individual woman may see smaller or larger changes from week to week.
You can see that average body weight is changing from week to week during the month with the lowest value occurring in the early follicular phase and the highest in the late luteal phase. I might go so far as to suggest women avoid any measurement during the last week of the cycle due to the large increase that can occur which can be extremely psychologically stressful. In practice that would mean only tracking for three weeks out of the month. Perhaps the bigger point of the table is that comparing any individual week of the cycle to any other individual week is rather pointless due to the water weight shifts that are occurring. Weight goes up from the early to late follicular phase, goes down to a different number in the early luteal before increasing again in the late luteal phase.
The week-to-week shifts in hormones and body weight make any comparisons useless. The same holds for other body composition methods.
At the same time, you can see that it is possible to compare one week of the month to the same week of the following month. Bodyweight or BF% could be compared between the early follicular phase of Week 1 and the early follicular phase of Week 2 and this will give some indication of what is actually happening over time. The same would hold for the late follicular to late follicular, early luteal to early luteal and late luteal to late luteal. So from Month 1 to Month 2, body weight goes down 2 lbs in each week of the phase. The numbers are all still different from each other but the absolute change is the same. I've shown a similar result from Month 2 to Month 3. The changes might not be this consistent in the sense that every week might not show the same 1 or 2 pound loss and I'd expect the late luteal phase to be the most variable. But overall, comparing only like weeks of the cycle to each other will give a much better indication of what is happening than trying to compare weeks within the same month.
This does raise the question of what a woman's "real" weight or BF% both for her own peace of mind as well as within the context of the calculations that will appear late in this blog. That is, which week's numbers should a woman use when setting up her diet or protein intake or what have you? In one sense it doesn't matter so long as the same week of the month is used to make any changes. In another sense, since any increase in water weight from week to week isn't "real" in the sense of representing a true change in body composition, measuring in a week where water retention is known to occur makes no sense. As water retention is likely to be at its lowest during the early follicular phase, I'd generally recommend using the average body weight, BF% estimate, from that week. Usually weight will be at its lowest roughly 3-4 days following menstruation and this would give the best indicator of a woman's true weight. There is another reason that using the early follicular phase to set up a diet is important related to when it's best for the normally cycling woman to actually start her diet.
How Often Should Measurements be Taken?
The final question I want to address regarding tracking body composition is how frequently measurements should be taken, either for general tracking purposes or to know when some aspect of the diet may need to be adjusted. In general, outside of the daily weighing/rolling average I described, most people probably take measurements too frequently. Even with the scale, this is true and people will weigh when they wake up, before and after they go to the bathroom, with and without clothes, in the evening with the goal of getting the lightest weight possible (this is of course the correct value). At any gym you can see dieters weighing before and after the workout to see how much they've lost. Even with other methods, people go a little bit nuts. They'll break out the calipers or tape measure daily or multiple times daily and just drive themselves crazy by doing so. Measurement error and the small day-to-day changes I described make this pointless and even actual body composition changes are far too slow for this to be useful.
The only possible exception to the above is the very lean Category 1 female who is nearing the end of her diet where appearance and even skinfolds may be changing very rapidly. This will never happen in the Category 2/3 female and the reason has to do with the total amount of fat being lost relative to how much is left to lose. A 130 lb female at 14% body fat with 10% essential fat only has 4% fat or 5 pounds of fat that she can lose. A half-pound fat loss represents 10% of that value and the measurable or visible changes may be profound. In contrast, a 200 lb female at 40% body fat with 10% essential fat has 60 lbs of fat that she could potentially lose. A 2 pound fat loss is only 3% and simply won't be visible or measurable. But outside of that singular population (lean Category 1 females), obsessive and constant measurement only adds to the inherent stress of dieting.