Weight swings

Reasons behind weight fluctuations

Do you sometimes step on the scales, after a week of eating well, and wonder where you went wrong? Have you ever weighed yourself the morning after a big night out and despaired about how it can take a week to lose 0.5kg but only a few hours to gain 2kg? This week, we explain the reasons behind these unfair fluctuations.

The good news is it’s almost impossible for that extra weight to be fat. True weight gain is slow, just as true weight loss takes time. Remember, a kilo equals around 7,000 calories, which means if you burn around 1,800 calories every 24 hours (check your diary for your average daily burn) you would have to consume more than 8,000 calories in a single day to gain an extra kilo of fat.

So what’s happening? What causes your weight to drop one day and shoot up the next?

The most likely culprit is water but there are a few other elements involved as well. When you get on the scales you don’t just weigh your organs, muscles, bones and fat, you weigh everything in your body at the time, including the water in your system, the liquids you’ve recently taken in, and the undigested food you’ve eaten. It’s these last three things that can cause the big fluctuations.

Water torture

A glass of water weighs around 250 grams, drink it and there will be an immediate impact on the scales. Add some salty food into the mix and chances are you’ll see some even higher numbers – sodium is like a magnet for water, it attracts and holds onto it.

There are other things that encourage your body to hold on to extra water as well. For example, some medications, such as high blood pressure and anti-inflammatory drugs, can have an impact. Hormones can also play a part – the ebbs and flows of female hormones throughout the month are often mirrored by the ebbs and flows of water retention. Ironically, not drinking enough water is another cause of water retention. When your body feels dehydrated it starts to hold onto whatever liquid it can get.

Building reserves

Glycogen is your body’s store of carbohydrate in the muscle and liver. When the body puts that carbohydrate away for later use, it packs a lot of water in at the same time. In fact, it’s estimated that your body can hold approximately 0.5kg of glycogen along with around 1kg to 2kg of accompanying water.

Your body constantly uses and depletes this store of carbohydrate and water. When you are in weight loss mode, your reserves will be low most of the time. Then, when you refuel or have a blow out, your body replenishes these stores along with the liquid. Weigh yourself when your glycogen stores are low and you are going to get a much lighter result to when they are topped up. This is not fat but a fluctuation brought on by your body’s natural processes.

Food weight

Step on to the scales holding a sandwich and you’ll weigh more than if you were empty handed. Eat the sandwich and you’ll carry its weight until it is digested. It’s important to remember that food weight and calories are not the same thing – eat a kilo of butter and you will probably gain real weight because it’s equal to around 7,000 calories, eat a kilo of lettuce and you’ll only hold onto the extra weight for the time that it takes for it to work its way through your system and come out the other side.

Working it off

Exercise actually combines water loss from perspiration and respiration with glycogen loss. Straight after a workout your weight is likely to be down, but these good numbers will probably only last as long as your next drink, your next meal, or both.

Dealing with upsetting fluctuations

The day after you’ve had a night off your healthy eating plan is probably the worst time to weigh yourself. Depending on the amount of sodium in your meal, you are likely to be retaining water, along with the extra weight from undigested and un-eliminated food. If you are going to get discouraged, stay away from the scales for a couple of days after a night off. If you do check your weight and see a depressing result, remind yourself that there are other factors at play.

For those other times when there seems to be no reason for the fluctuation, think about what’s been happening the previous few days: are you constipated, have you eaten something salty, were you dehydrated the last time you stepped on the scales? Check your diary, because real weight gain and weight loss is all about calories. If you have tracked your energy equation and you have not eaten an extra few thousand calories that week, the only reason for your weight gain will be food or water weight.

Tips for weighing in

• Use the same scales at the same time each week – and wear the same clothes, or none at all
• Take your waist measurements on a weekly basis. If the scales go up but your waist measurements stay the same you know it’s fluid rather than fat you’re holding.
• Check your energy balance using your diary – it’s a fantastic predictor of weight gain.