Honestly? The short answer is more than likely that you are consuming more calories than you are expending.
Of course there is a little more to it than that. It helps to know what type of exercise you are doing, how long you are doing it for, and at what intensity. But, for the vast majority of people, it is not the exercise part that matters most. It’s what you eat. When it comes to weight loss, a good diet trumps exercise every time.
How much are you eating?
It might not be an easy truth, but study after study shows that people consistently underestimate the amount of calories that they consume. They forget the handful of nuts, or the cans of soft drink, or even just the fruit to tide them over to tea. Research from Harvard Medical School published in the BMJ found that, of more than 3,400 customers polled at fast food chains, more than a quarter underestimated calorie content by at least 500 calories. And over time that adds up – along with the pounds.
Another thing worth considering: as well as underestimating calories consumed, most people tend to overestimate how much they burn through exercise. In a Canadian study, a group of recruits were told to eat the number of calories they thought they had just burned by working out. They ate two to three times as much.
Exercise is not a magic bullet. You can’t – and I speak, with regret, as someone who runs about 60 miles a week – use it as carte blanche to scoff whatever you want. A 2011 study in the American Journal of Medicine put it starkly, “isolated aerobic exercise is not an effective weight loss therapy”. If you want to lose weight, you must first and foremost examine your diet.
But I’ve worked up quite an appetite!
Our relationship with food is complex. Many of us – again, myself included – use treats as a reward. We think a long session in the gym, or a long run or bike ride, deserves a large plate of food as a reward. Yet much of this is in our heads, rather than our growling stomachs, and indeed exercise can actually be an appetite suppressant.
This is illustrated by another Canadian study dating from 1997. Three groups were chosen. One did high-intensity cardio, one low-intensity cardio, and a control group no exercise at all. The researchers asked all participants to then rate how hungry they were, before taking them to an all-you-can-eat buffet. There was no statistical difference either between how people in the various groups rated their hunger, nor how much they ate. In other words: no one actually worked up an appetite.
(An aside: swimming always strikes me as the worst “culprit” for this. Wonderful though swimming is, it almost always seems to make you starving afterwards, even if you’ve done very little other than sedately paddle around. Swimming in cold water, rather than an overheated pool, does burn more calories – because your body is working harder to keep warm. However, it also stimulates your appetite more – by up to 44%. So it’s pretty easy to consume more than you’ve burned after a swimming session. I love swimming and it has many other benefits, but as a fat or weight loss tool it is less effective than other forms of exercise.)
So what are you eating?
Another answer to the question is to look not so much at the amount you eat as what it consists of. Not least because some foods have a higher “satiety index” than others, and will therefore leave you feeling fuller for longer. A protein-rich diet – with about 35% of your calories coming from a protein source – seems to be the best way to combat hunger, fight muscle loss and generally feel smug and healthy.
This is not to buy into the “carbs are evil” myth. Carbs are an important part of a balanced diet, particularly if your chosen form of exercise is endurance-based. On the flip side, however, people who think they need to “carb-load” before endurance efforts should be aware that the body has more than enough stored in it for a good 90 minutes of exercise before you need to start thinking about topping up with gels or similar.
One in, one out?
Your heart rate monitor informs you you’ve burned 500 calories. A large bar of chocolate is roughly 500 calories. Ergo, you can eat that (in addition to everything else you’re having) and not gain a pound, right? In truth, the trade-off is a more complicated than that.
In a study published in 2010 in Medicine and Science in Sports and Exercise, researchers at Louisiana State University recruited three groups of moderately overweight volunteers. One group as control, the second group cutting calories by 25%, and a third by 12.5% but increasingly their calories burned through physical activity to the same level: so the two latter groups had the same overall calorie deficit. What happened? Well, both group lost the same amount of weight. But the group who followed the 12.5% less calories/more physical exercise improved other health markers – like cholesterol, blood pressure and insulin sensitivity. So, essentially, while a calorie is a calorie, and while diet is far more important for weight loss, you should exercise too – because it’ll improve your overall health.
The myth of the fat burning zone
Anyone who has ever been on a “cardio” machine in a gym will have seen those heart rate graphs. You know, the bit with the “weight management” or “fat-burning” zone. Those who believe fervently in those graphs seem to worry that pushing themselves higher than that zone could have positively deleterious effects on their fat burning.
Sorry, but it doesn’t work like that. The fat-burning zone is based on a misunderstanding of how our bodies work. When we exercise, we use both fat and carbohydrates stored in our cells. At a low level of intensity – a walk or gentle cycle ride – we burn more fat than carbohydrate. If we push harder, and longer, the proportion changes, switching over (dependent on fitness and age and so on) at about 60% of your max heart rate. This does not, however, mean we stop burning fat – or even burn less fat – when we go at it harder than that.
Yes, the ratio shifts, but at a higher intensity/duration you are burning more of both anyway.
And there’s more bad news for those who believe in the fat-burning zone.
If you burn mostly carbohydrate during exercise, then when you eat afterwards, your body will convert those calories into carbohydrate to replenish what you’ve used. If you burn mostly fat, your carbohydrates stores will still be full. So, with no need to top them up, your body will store those calories as fat – rendering your fat-burning efforts pretty redundant.
Just look at sprinters. They do much of their training at a very high intensities with long rest periods. I’m pretty sure they are almost never in that fat burning zone, either on the track or in the gym. They generally look like they are coping OK with keeping the fat at bay…
But muscle weighs more than fat!
No, it really doesn’t. A pound of muscle weighs – who would have thought it? – a pound. The same as a pound of fat. Or a pound of lemon jelly. Or a pound of sweets. A pound is a pound. The muscle just takes up a bit less space (don’t click on this visual representation if you are squeamish).If the scales are unfavourable to you, it’s unlikely to be because the 20-minute run you did yesterday suddenly added 3lb of muscle to your frame. Sorry.
Keeping it off
The trouble with losing weight is that the less you weigh, the fewer calories you need to sustain you, on a day-to-day basis. This is one of the (many) reasons that people might find initial weight loss quite easy – but then hit a “plateau”. Equally, it’s why many people “finish” a diet, then immediately find they are putting weight back on: they are eating what they used to be able to consume while maintaining the same weight, but now they actually need less. It doesn’t seem fair, does it?
OK, so what exercise should I do?
Which is best for weight loss? The honest answer is probably “the one you enjoy and will stick to”. Cardio burns more calories at the time you are doing it, but weight training encourages your body to burn more calories through the rest of the day. Most studies that have examined the issue tend to conclude that, if weight loss is the goal, the best approach is to do both.
Finally, for far more authoritative, in-depth analysis of fitness myths and weight loss confusion, I cannot recommend highly enough this book by Alex Hutchinson. In an industry (or industries – both the diet and fitness ones in this case) that seem to thrive on fads, misinformation and peddling the latest “must have” regimes or gadgets, it’s a clear, science-based look at what really works.
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