Why diets don’t work in the long-run

For many people, losing weight involves going on some sort of diet. The idea behind diets is to consume fewer calories than you expend, which will lead to weight loss over time.

But the problem with diets is that they cannot produce long-term results alone, unless you maintain that lower calorie count for good. This is because the body adapts to weight loss in ways that you wouldn’t necessarily expect.

The science

We all have a “natural” weight range that we generally regress to, known as the set point. This is affected by our genes, behaviour and environment. If left to its own devices (i.e. with little deliberate input from us), our body will bring us back to or sustain us at that set point through a variety of biological driving factors. Consequently, when we lose weight our body adapts in a way that would predispose us to regain that weight, unless we change our habits.

Warning signals

When we lose a significant amount of body weight, our adipose (fat) stores reduce in size. This means that various signals are sent to our brain – particularly to the hypothalamus, responsible for the regulation of bodily functions. These signals are sent from our fat stores and digestive system, communicating that our energy stores are shrinking and fewer nutrients are available. Our hunger, activity levels and metabolic processes are subsequently altered in order to keep the body stable, by storing and conserving nutrients instead of using them for energy.

Star, Golden, Christmas, Connection

Take leptin as one example, a hormone that influences our appetite. The amount of leptin in our systems depends on the amount of body fat we have. When we lose weight we therefore have less leptin, which in turn makes it harder for the body to detect when we are full .

This is a natural evolutionary phenomenon, and in the days of the caveman it was instrumental in preventing us from starving. However, it is not just an extreme starvation reaction. It occurs regardless of the weight you started at, and regardless of the state of your body when you finish losing weight.

Lower energy requirements

As our body weight decreases, the energy we require to function at rest and during physical activity also decreases, simply because there is less of us. For this reason, we burn fewer calories in total.

In addition, we burn fewer calories through digestion, because we are eating less. While this particular metabolic activity makes up a very small portion of total daily energy expenditure, it still contributes to the other more significant adaptations that altogether result in a lower metabolic rate.

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For example, let’s say that one particular person would have to consume 2500 calories daily to maintain a weight of 15 stone, and 2100 calories to maintain a weight of 12 stone. [These are just figures I have plucked out of the air for demonstration purposes, and this is a basic scenario!] If that person reduces their weight from 15 to 12 stone through a calorie-controlled diet, and wanted to maintain it that way, they would have to to eat just 2100 calories daily – they could not return to their previous consumption of 2500 calories without regaining the weight.

There is no reset button!

Unfortunately, our appetites do not adjust to suit this lower body weight, and our metabolic rates do not revert back to the way they were at the higher weight. Our “set point” weight is not changed. So unless you are going to indefinitely restrict your calorie intake, dieting isn’t going to get you the results you want.

The extent to which these factors come into play is also affected by genes, so some people will unfortunately find it harder than others to keep the weight off after having lost it.

If you are interested in finding out more, the details are all in the two articles referenced at the bottom of the page (MacLean et al., 2011; Rosenbaum & Leibel, 2010). There are plenty of excellent scientific articles out there, but these are particularly good as they integrate and review the evidence available.

So what’s the alternative?

You can probably see why it isn’t surprising that our conscious attempts to restrict our food intake often fail in the long-run. We are literally fighting against the very biological signals that are designed to keep us alive, which operate beneath our awareness!

Not to mention that with dieting we are actually more likely to re-gain any weight lost, develop unhealthy obsessions with food and become unhappier than we were in the first place.

This means going on a diet in order to lose weight for good is not the solution. What sustainable weight loss comes down to is being more active and addressing your habits. Your energy requirements are inevitably going to reduce as you lose weight, therefore the only way to maximise them is to be more active, and hence use more energy. As humans beings we are designed to move, and the benefits of exercise are almost endless. Also, as I will explain below, it isn’t about arbitrarily restricting your calorie intake or cutting out certain food groups – it’s about identifying your strengths and weaknesses, then changing your lifestyle for good.

Here’s what you can do:

  1. Find a form of movement that you love. There is a reason I choose the word “movement”, and that is because any continuous form of movement counts as “exercise.” It shouldn’t be seen as a chore you just want out of the way; exercise is inherent in many activities, such as playing football in the park with your children, playing sport in general, gardening, walking or playing tennis with a friend, to name a few examples. You can even burn a surprising amount of calories doing housework.

    You don’t have to hit the gym or go for a run if you don’t want to – any movement is good! [You’ll reap extra benefits by doing some sort of strength-training, as lean mass (muscle) requires more energy than other tissues, HOWEVER this effect is not as significant as often described.] By including regular movement in your routine, you will increase your daily calorie expenditure, so you needn’t be so strict with your diet. Not to mention you will reap the many benefits of physical activity, which will contribute to your overall well-being.

  2. Identify the problem areas in your daily diet. By “diet” in this case, I mean what you generally eat at the moment. It is usually not food itself that is the problem, but the psychological reliance we have on foods and our habits. Is there a particular food you often find yourself eating far too much of? Do you restrict your intake in the morning, only to find yourself over-eating at night? Are the staple foods in your diet nutritious? Do you have any habits that make healthy choices harder and unhealthy choices easier to make? The same applies for the things you are doing well already – identify those and build on them. By adjusting small components of your diet one at a time, you can create a surprisingly large change with little effort. No one type of food is the problem.
  3. Practise mindful or “intuitive” eating. Learn to identify feelings of both hunger and fullness, and pay attention to how your body feels in response to different foods. It takes some practice, but being more in tune with the way you feel can help you make better choices and eat foods that make you feel energised. Here I must direct your attention to a brilliant TED talk by neuroscientist Sandra Aamodt: https://www.ted.com/talks/sandra_aamodt_why_dieting_doesn_t_usually_work?language=en – she talks with great knowledge and wisdom about the various problems with dieting, and discusses her own experiences which many people will relate to.

If you follow these three steps, you will be able to create a lifestyle for yourself that allows you to achieve your goals and enjoy life in the meantime. Focus on being more active and changing your habits around – this will soon become second nature. This way you avoid the constant psychological struggles or yo-yo weight loss that often come with dieting!

References

MacLean, P. S., Bergouignan, A., Cornier, M-A., & Jackman, M. R. (2011). Biology’s response to dieting: The impetus for weight regain. American Journal of Physiology, 301, 581-600. doi:10.1152/ajpregu.00755.2010

Rosenbaum, M., & Leibel, R. L. (2010). Adaptive thermogenesis in humans. International Journal of Obesity, 34, 47-55. doi:10.1038/ijo.2010.184

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