Why Dieting isn’t Scientific

Humans are not machines and we do not all respond in the same way

There are a lot of claims in the media around different dieting approaches being “scientific”. But humans are not machines and do not all respond in the same way. Unlike scientific experiments, where you can reproduce the same result under the same conditions, this doesn't hold true for humans and it's one of the challenges around studying medicines because we can’t always explain why some people respond to some treatments and other people don’t.

Eating is not as simple as refuelling and burning the energy consumed

Nutrition and eating in particular is not like filling up the car and using up the fuel. We know that its not as simple as calories in and calories out. We know that there are different benefits of foods beyond their calorific value and the nutrients they provide the body, which is fairly well accepted.

The population is key in any dieting claim

Randomised controlled trials are regarded as the gold standard evidence that an intervention works in the medical industry. In any clinical trial, there is a defined population who we studying. A group of patients are selected and allocated to either the new treatment or the usual care, often without knowing which one they are getting. The key here, is that these studies are designed to select the population who are the most likely to benefit. In studies of any diet, the population may be those who want to lose weight to look different versus people who need to lose weight because of some health risk. So the diet might work for those people, but it doesn’t mean it will work for everyone.

Data gathered in health apps depends on who downloads the app

Clinical studies are often done in patients with other conditions, like diabetes, and the weight loss is shown to have a positive impact on their medical condition.

Data gathered in health apps does not necessarily have the same population as those who participate in clinical dieting studies. These apps are often used by people who are more health conscious and therefore more motivated around eating healthily. Data presented from these apps as “scientific” is therefore somewhat misleading because the people decide themselves to download the app and also decide what information to provide, rather than it being objectively assessed.

Baseline is an important consideration in any dietary intervention

When following a given diet, its effectiveness depends on how much change you are required to make compared to before. So for example, if you switch from eating normal foods to just having soups and shakes, the impact will be greater. Also if its the first diet you have tried, you are possibly more motivated than if you are a serial dieter.

Anything can work for a short period of time

Participants in clinical trials of diets are followed for a finite period of time. Some diets claim that you can lose 2 stone in a month or drop a dress size in a fortnight, are based on following a restrictive regime for a specific number of days. Its very easy to claim something works, if its only done for a short period of time but it is less compelling to sustain the weight loss. The reason people don’t stay on diets for longer is that the regimens are too restrictive or they don’t match people’s usual eating habits. People lose motivation and the weight that has been lost, is often regained.

When people are monitored on a diet, they behave differently

People behave differently when they are being watched (observer bias) and this is especially true for dieters. If we know we are going to be weighed, we will probably be more conscious about what we are eating. If we know that we have to record what we are eating, we may make different choices. So of course, when we are following a diet our behaviour is different because we have a greater awareness of what we are eating. This positive effect is why diet groups work at effecting and encouraging people to continue with their weight loss programme.

We want to believe that we can achieve what others have done

Social media has compelling pictures about someone who has managed to lose 5 stone, which makes us think if they can succeed then so can I. But the reality is that we may not have the same characteristics (population), we may have started at a different point (baseline), the programme they followed may not be sustainable, their reality may not be our normality and without the support or pressure to succeed (observer bias), we often lose motivation to continue.

What matters is finding out what works for you

When we consider “scientific claims”, we need to be careful that we are not putting more credibility onto evidence that is seen as robust because of its design. If it doesn’t match reality, it doesn’t matter if it works in ideal conditions. What matters is that people are empowered to understand what is driving their overeating and finding a place of balance.