Key Question: I diet and exercise... but why do I struggle to lose weight?
As we know from Article #2 weight gain is caused by a long-term excess of calories, where energy intake is greater than energy expenditure. For this reason, diet (a decrease in your energy intake) and exercise (an increase in your energy expenditure) could be potential weight loss solutions, because they both create a calorie deficit.
For some people, diet-based interventions can be more successful than exercise interventions for weight loss in the initial months. Dieting (if well planned and implemented) can also result in long-term weight loss for many people. However, with diet-based interventions many people also gain weight back (e.g. 1-2 years later). This is because changes in our bodies and in our behaviors can occur, including a reduction in our energy expenditure due to a decrease in our body- and muscle-mass and therefore in our resting metabolic rate (see Article #2) and changes to appetite-regulating hormones, which can make us hungrier. This is in line with a theory that the body doesn’t want to lose weight, because our genes were selected during the hunter-gatherer period, when we wanted to be good at energy storage when food was available, but also good at conserving fat stores during periods when we couldn’t get food. The response of the human body to a calorie deficit means it is harder to maintain a large gap between energy intake and energy expenditure in order to lose weight in the long run. Put simply, your body doesn’t want you to lose weight!!
It has been suggested that being physically active may help with maintaining weight loss, partly because exercise can alter some signals about weight loss that feedback to the brain and it can also help to preserve muscle mass during weight loss, thereby maintaining our resting metabolic rate (and energy expenditure) at a higher level (see Article #2).
So, for weight loss is the answer to do more exercise? Well, for most people typical exercise will create a relatively small calorie deficit. For example, 50 minutes of continuous cycling can create a deficit of only 300-400 calories. When performing sessions four times a week that would be ~1200 calories, which is a small amount of energy and could be nearly wiped out by a few pints of beer (~400 calories) and an extra burger (300-400 calories) at a BBQ. If this is combined with a reduction in non-exercise physical activity (e.g. you may drive to the shops instead of walking because you've done your run!) it will mean a modest initial weight loss when you start an exercise regime, especially compared to diet-based interventions.
One big problem is that many people have unrealistic expectations regarding exercise and weight loss, and fail to achieve their unrealistic goals. Therefore, self-efficacy (the confidence in your ability) for weight loss and motivation can be reduced, which increases the likelihood of you giving up, which may lead to weight regain. A review published in 2018, concluded that people 'seeking to lose weight without changing their dietary habits need to be counseled that high PA levels (225–420 min/week of exercise) are necessary to achieve clinically significant weight loss'.
So should I just give up? Of course not!! Firstly, exercise and diet in combination can create successful weight loss for many people and the trick is also understanding that weight loss through diet or exercise is a long-term goal. Therefore, try to combine diet with an increase in your physical activity and find a lifestyle routine that you can stick to for a long time.
It is also worth remembering that exercise causes a HUGE array of health benefits even without weight loss. One of my favorite studies in The Journal of Physiology showed that when you overeat by 50 % more calories than normal, performing exercise (even when the calories burnt from exercise are also added on) many of the bad health changes in the body are prevented. Whilst I am DEFINITELY not suggesting you eat that much, this goes to show the power of exercise for your health.
The take home message: Exercise and diet can be successful long-term weight loss strategies but changes take time. Find a routine that you can stick with, as compliance to an healthy lifestyle routine is a strong predictor of long-term success.