Fitness, BMI, & PKU

Many of us with PKU, or other chronic conditions, will have our body measurements are taken at regular clinic appointments. Body weight is one aspect which is considered when setting personal treatment regimes for PKU and other metabolic disorders. This means I have a fairly extensive record of my weight for over three decades.

I try not to obsess, but living with PKU means my weight is regularly discussed. Throw in the messages, conscious and unconscious, about weight from society in general, and you quickly see that we deal carry a greater burden of weight issues than many.

I try not to obsess, but living with PKU means my weight is regularly discussed.

Losing weight vs losing fat.

One memorable occasion, I was quietly confident before stepping on the scales. I’d joined a gym and been fairly active since then. My clothes were loose and I felt stronger. I was sure I had lost weight. The only question was how much I had lost.
Nothing. The scales said both my weight and BMI had gone up slightly. But how!

Another PKU patient, Kate Buckland, reported a similar experience in her piece for the Nutricia website: “Last year doing bodyweight High Intensity Interval Training I lost almost 3 dress sizes, 8% body fat and… 1.5 kg. People kept commenting on how much weight I'd lost, but I hadn't lost weight. I had lost fat and gained muscle, which is awesome!”

Beyond BMI

Many health experts believe BMI has significant limitations. The NHS states that "The BMI calculation is just one measure of health. It cannot tell the difference between muscle and fat."

Essentially, BMI measures if you are carrying too much weight for your height, but it can’t tell you if that weight is excess fat or excess muscle. This is why athletes and gym bunnies are sometimes classed as obese under the BMI system even though they don’t have too much fat.

Suggestions for new measurements include the waist to height ratio. This is also known as the body roundness indicator, or BRI. This is a factor of your height, weight, and waist measurement. Fortunately, there is a body roundness calculator to help us.

Remember that many of us with metabolic disorders are already on a restrictive diet.

Safe weight loss and PKU diets

It is widely agreed that losing weight quickly is not a good idea. ‘Yoyo dieting’ is sadly common, when we work hard to lose weight only to gain it all back. Slow and steady changes in habit and lifestyle are the best way to lose weight. The NHS says we should be aiming for a safe rate of weight loss "between 0.5 and 1kg per week".

Wait! Remember that many of us with metabolic are already on a restrictive diet. We already pay attention to what we eat, and generally don’t have the quick gain of cutting out weekly visits to the kebab shop.

We also need to remember that losing weight is a slow process, just as putting it on can be. My health records tell me that the last time I was in the healthy BMI range, the first iPhone had just been released. I do plan to get back to that weight range, but need to recognise that it will take time!

Getting started on getting fit.

I don't just want to lose weight, in fact, that isn't my main goal. My joints are creaking a bit, and my muscles are a little weaker. I simply want to feel healthier, and that means moving more, too.

The NSPKU race to £10K inspired me to pick up the running shoes again. And I have a personal goal for a sponsored walk in memory of a friend planned for the autumn. All this means I would like to feel fitter. That journey will be planned in part two of this blog — coming soon. 😄😄