Do more, eat less - that's the secret to success
When celebrities are asked in interviews what they did to get their body ready for a particular movie role, a common answer comes up.
"It was 20 per cent exercise, 80 per cent diet," they'll say.
A study published in Annals of Behavioral Medicine by Stanford University researchers looked specifically at this notion and found it to be true: For best results to improve your body shape, you need to change both your exercise routine and your diet at the same time.
Some doctors and nutritionists recommend that you only undertake one change at a time to avoid feeling overwhelmed.
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However, the Stanford study found that taking on a new diet first can actually interfere with establishing a consistent exercise routine.
Undertaking an exercise routine first can be a good place to start, but you may quickly become disenchanted with it if you don't see results, and not even start the diet.
Therefore, the study found, those who do a "double hit" from the beginning are most likely to stay motivated and maintain good diet and exercise regimens over the course of one year.
Let's look at how diet and exercise work together on a physiological level, as weight loss and gain depends on two simple things: Energy consumption (diet) in, and expenditure (exercise) out.
To gain weight (in muscle, for example) you need to consume more calories than you're expending, though they must be the calories from food your body can use efficiently in this process, such as protein, some carbohydrates, and some types of good fats.
To lose weight, you need to burn off all the calories you consume each day, and then some. As every day, week, and month goes by, this process of burning off more than you're consuming will shed your fat because you're creating a deficit.
To lose, say, one kilogram per week, that deficit needs to be around 1800 calories (7500 kilojoules, or three Big Mac's worth) below your energy intake for that week. When you reach a weight you're happy with, you can then start consumption and expenditure in equal "maintenance" amounts.
One of the problems with this concept of energy in versus energy out, however, is tracking it all. A study from the International Journal of Obesity and Related Metabolic Disorders found this to be a key flaw in researching how diet and exercise work together, as research subjects tend to underestimate their caloric intake, and overestimate their expenditure through exercise and daily living.
Fitness trackers such as the Fitbit and Apple Watch have made this process easier, though it's still not flawless.
To look back at the "20 per cent exercise, 80 per cent diet" effort mantra, the reason the latter is so important is because humans use up the majority of the calories they consume simply by going about their day. When we sit, walk, work, and sleep, we're burning energy. In fact, we even burn energy while we're actually eating.
Exercise, on the contrary, contributes to a relatively small amount of each day's energy expenditure. In a one-hour gym session, for example, you might only burn 500 calories (2000 kilojoules), which is slightly less than the equivalent of one of those Big Macs.
When you exercise regularly, though, you speed up your metabolism and for every minute of every day – awake and asleep – it is burning energy more efficiently. Even though only 20 per cent of your efforts go into exercise, you'll reap the benefits without any extra work.
Once you're keeping that metabolic rate high, what you do with the other 80 per cent remains crucial. Hence diet and exercise being so important together as a team.
People often fail at improving their body composition because the diet side of the equation is harder and requires more discipline. Exercise produces endorphins, and makes you feel fantastic; being on a diet makes you feel restricted and life can seem less enjoyable.
This is why it is key to do both together. When you are more physically active, you feel better about yourself, and you're less keen to put unhealthy food into your body. This makes staying on a diet (and potentially making it a lifestyle choice) more enjoyable from the outset.
Because diet alone can't tone or strengthen your body, the double hit also ensures you're not just losing weight, but getting stronger and shapelier, too.
Lee Suckling has a master's degree specialising in personal-health reporting. Do you have a health topic you'd like Lee to investigate? Send us an email firstname.lastname@example.org with Dear Lee in the subject line.