The connection between junk food and obesity seems obvious.
With foods like candy, fast food and soda so readily available, it’s natural to assume that these foods are a key factor in the obesity epidemic that is sweeping the United States.
Certainly, we do tend to eat much more of these foods than we should – and people often eat junk food instead of food that is healthier and nutrient filled.
You can also see this assumption about junk food and obesity in policy.
For example, there is growing interest in the development of a sugar tax, which could significantly increase the price of foods high in sugar, particularly sugary sodas (1).
But, it turns out that the connection between junk food and obesity isn’t really as simple as we assume.
In particular, there was one recent study that examined the factors that contribute to obesity, and it found some unexpected outcomes.
The Study Itself
The study made use of data from the National Health and Nutrition Examination Survey, which involves 5,000 surveys across the United States. The design of the survey focuses on obtaining a representative sample and uses a number of approaches to promote accurate information.
For their study and analysis, the authors excluded people who were underweight or morbidly obese and people who did not provide all the required information. This gave a total sample size of 4,895. Participants were then broken up into BMI subcategories (a measure of body fat in relation to height).
The authors found a number of important results from the study.
One was that there wasn’t a significant difference in how often people ate fast food or ate away from home across the different BMI subcategories.
Likewise, there was no significant variation in consumption of soft drinks (full calorie), desserts or French fries.
The authors did find a significant variation for snacking (both sweet and non-sweet snacks), but this relationship was negative. This means that people with higher BMIs tended to snack less often than those with lower BMIs.
That could be because people who were overweight were more aware of their eating habits, or it could be the result of some other unknown factor.
The authors did also note that in general the higher BMI categories tended to have significantly less fruit and vegetable consumption, although that pattern wasn’t true for overweight people in relation to fruit consumption.
Strengths and Limitations
The main strength of the study is the sample size. It also helped that the sample was designed to be representative, so the observed patterns are likely to apply across the population.
One key limitation of the study was that it looked at the frequency of consumption, not the amount.
This means that there could still be a relationship between junk food and body weight if people with higher BMIs tended to eat more junk food per sitting.
As I’ve mentioned in the past, the observational nature of this study is also a limitation.
That limitation is very relevant in this case because people’s behavior concerning food is often different depending on their weight and their health. What’s more, people tend to lie on surveys about food, as NPR points out.
The authors did as much as they could to take variation in behavior into account, but an observational study design is still limiting.
Nevertheless, this type of research would have been difficult to do in an experimental setting.
It is also important to note that this study excluded people who were morbidly obese and those were clinically underweight, so the observed patterns may not apply to those groups of people.
These populations were left out of the study because people who fit into those groups often engage in more extreme behaviors, which could influence the outcomes of the study.
Additionally, people who are morbidly obese or underweight should talk to their physician about how to get back to a healthy weight, as those situations can involve many complicating factors.
The basic results of the study were that in most of the sample population there was no correlation between consumption of candy, soft drinks or fast food and BMI.
Often, weight loss advice focuses on how people should cut down junk food in order to lose weight.
That advice is frequently given by health care professionals, and there is often an assumption that people who are overweight must be eating a significant amount of junk food.
In many cases, people feel that if they simply cut out junk food altogether, then they will lose the weight.
The outcomes of this study suggest that these assumptions may not be true.
That conclusion actually makes a whole lot of sense.
Successful weight loss is strongly connected to using more calories than you take in.
Junk food tends to be high in calories, so it does play a key role in this equation.
However, there are other factors that are equally important.
As the study points out, things like snacking frequency and how many calories a person consumes overall are just as relevant for weight loss.
Indeed, weight loss advice that focuses mainly on problem foods is likely to be ineffective, because people often end up consuming more calories than they mean to.
After all, there are so many foods out there that seem healthy but are actually as high in calories as junk food. And, as Everyday Nutrition points out, the marketing around such foods is often misleading.
The authors also commented that people may engage in compensatory behaviors.
So, a person might cut down on junk food to try and lose weight, but they may end up increasing their calorie consumption in other areas unintentionally.
This research reinforces the idea that one of the key approaches for weight loss is simply being aware of the calories you are taking in, regardless of their source. Simply recording what you eat can be the first step in this direction as it helps to increase your awareness of your patterns surrounding food.