The FastDay Forum

I've always had a healthy BMI but it was in the upper range of healthy when I started 5:2. It has now dropped to 22.15, and might go a bit lower during 2014, but these last few days I started to wonder whether this should be my minimum.

I have felt a bit more tired than usual, bit light headed, not feeling like doing any exercise, quite cold and I actually stayed home from work today because of all that. I had lean beef last night and don't think my iron level is too low. Could I have overdone it? There are others on this forum with much lower BMIs so perhaps my body has had to adjust too much too quickly.

Is a low waist to height ratio more important than a goal weight or healthy BMI?

I think it depends a lot on your build. I've stopped a bit short of goal (but within healthy BMI range) because I'm getting a bit bony in places.

I'm sure that others who are more knowledgeable than me will respond but I think that the 'right' BMI varies from person to person and you should listen to what your body is telling you. I set my target at a BMI of around 24 and although at the top end of normal I think it is right for my body at my age (51). I say it is right because I feel well, look slim and have been able to maintain it easily without fasting.

Hope you feel a bit better soon

From the waist up I am getting quite bony too but my thighs are still a reasonable size. I am hoping regular jogging might help there but today (and yesterday) I didn't have the energy. I think my body size is ok for a 46-year old but not yet slim.

[carorees]

Well some say that a BMI of 22 is the ideal regarding health risks, but of course BMI is such a blunt tool that you have to work out what is right for your body. If you have a large frame then you can add 10% extra, if a small frame then 10% less. If you are of Asian ethnic origin, unfortunately, you need to aim for a lower BMI as diabetes risks appear to be enhanced even at apparently normal BMI. I can't remember what the target is but I think the upper limit is around 24 (you'd need to check).

Probably the best measure is body fat percentage. The ideal body fat % depends on gender and age. For a middle-aged woman it should be between 20% and 35%. But where the fat is stored is important. Fat stored in the abdomen adds to the risk so really you should look at your waist:height ratio and your body fat percentage to work out whether you should try to maintain or continue to lose.

I'm lucky that I'm hourglass shaped so my waist reached half my height ages ago, when my BMI was still around 28. I have a large frame so even though my BMI is now 26, my body fat % is now below 35%. I set my weight target at 65kg which would put me at the high end of normal BMI, but correcting for my large frame would be equivalent to 22. I calculate that my body fat % should be about 30% at that point.


I worked my rough calculation like this:

Current weight = 71kg
Current BF% = 35%
71 x 0.35 = 24.85kg of fat (!!)
Therefore, lean (i.e., non-fat) mass = 71 - 24.85 = 46.15kg

Target BF% = 30%
Therefore if lean mass remains at 46kg that would represent 70% when the body fat is 30%
So 100% (i.e., target weight) is 46/70 x 100 = 65.9kg

Hope that makes some kind of sense!

In the end, though, as windsinger says, your body may have different ideas and so how you feel should be the most important measure. Your body will let you know when you get too low in weight by upping your hunger levels and making efforts to reduce your energy use (feeling cold, lethargic etc.). This is the 'famine effect'. Obviously if you are still overweight when this occurs you have to find a way to combat it by maintaining or even gaining for a little while, but if you are at a healthy weight then it's probably best to accept that as your proper weight and work to maintain.

Good luck with whatever you decide!

For reference, the upper limit of normal BMI for Asians is 23.

I don't actually care about BMI because I don't think it gives a particularly accurate picture, certainly not in my case. In spite of a low BMI I am still carrying a lot of fat round my middle whereas I have arms and legs like a stick insect. No one has ever said that thin arms and legs are a health risk but there is a lot of evidence that fat round your middle CAN be a real health hazard.

Ballerina x

Like other say, its upto you and how you feel. BMI is a crude measure. My BMI is just about in the normal range but my upper body is getting too bony so I've decided to stop and maintain hoping that the exercise will help reduce my hips/thighs as my weight stabilises

Carorees - do you have a special kind of scales that gives you your body fat %?

Two thoughts:

I wonder if studies of diabetes,etc risk among Asians used primarily (or all) subjects who have a slim build, and therefore should really have a lower BMI to account for their body types?

Asians are more typically short, and the standard BMI calculator is generous toward us short people (and harsh on the very tall). I know this is an unpopular stand to take (and I won't be suggesting it amongst my buddies in the short tent ) but it makes more sense for short people to use the "New BMI calculator":
http://people.maths.ox.ac.uk/trefethen/bmi_calc.html
There is a link on that page to the mathematics behind it.

I started 5:2 at a BMI of 25. Barely overweight. But the new BMI calculator gives me a BMI at that point of 27. Much closer to what was obvious to me looking in the mirror.

If you are an average height person, the two numbers will be virtually the same. This might be just too complicated, but I'm hoping that when @Moogie next updates the tracker, she will be able to allow users to employ either calculator.

@wendyjane, according to the calculator you linked to my BMI is 19.74 so not much higher than previously at 19.04 on the old scale.

Are you using the calculator that I provided the link to, @Callyanna?
Using your stats in your signature, I get 18.9 and 19.9.
Okay, not a huge difference. The difference for me at my target weight is 1.5 points.
But when the entire range of healthy BMIs is only about 6 1/2 points, I think that's significant.

Thank you all so much for taking the time to give me such considered advice. Having just read all the above, and considering that I am happy with my shape, I think I am going to try to maintain this weight and use exercise to tone, not to lose weight.

I am Caucasian, 1.77cm (5'10) so relatively tall and average built. I'm a pear shape. I've seen my mother and grandmother struggling with diets their whole life so It's important to find something that works for me as I approach menopause. I think 5:2 does but it has only been four months.

Wendy

hi again @wendyjane, hadn't updated my signature data to reflect another small loss, so down to 96 lbs so yes,I used the new calculator taking that into account.

Hmm... I think the Japanese healthcare people have been applying those Asian BMI ranges to Westerners at our annual health check. There's always a lot of dejected healthy looking people walking around saying things like 'obese! They said I'm obese!'

Wendy, I think I have a similar build to you. The trouble is if I lose more weight I have no guarantee about where it will come off. Like you, I am going to try maintaining for a while and continuing with exercise. Hopefully my weight will shift around a bit. Luckily my height to waist ratio is fine.

That's brilliant. According to the 'New BMI calculator' I'm still overweight.
I'm going to stay on maintenance though, at 68 years old I don't want to be any thinner, my face is already starting to look gaunt. It would be good to have slimmer hips and tummy but for me a thin drawn face would be more disagreeable than large hips.