Why is nutrition advice so confusing?

One of your training buddies tells you how they feel so much better on this new low carb, high fat diet then your other training partner is bragging about how they just nailed their race because of this high carb, low fat diet they are on. So, you decide to go and see what the researchers are saying, you find yourself even more confused because even they can’t agree.

If you find yourself confused about nutrition, don’t worry, you are not alone! There is over a third of the population confused about what makes up a good diet. Why can’t it be as simple as this is the diet that is healthiest and works, full stop. Why is there so much confusion? And why does it seem like the answers are always changing, one year a particular diet is the best thing and the next it could give you diabetes. Well, there’s a few reasons and we are going to chat about them now. Finally, we will provide some tips to help you become a more informed consumer of nutrition information and to identify nutritional nonsense.

Everyone has an Opinion on Nutrition

It seems if you win a race, run, ride or swim fast, put out more power than the next person, lose weight or gain muscle then you are sought out for nutrition advice. You talk about your nutrition approach, and this then becomes gospel to some people, even though you have no qualification in nutrition, in fact you are an engineer by trade. It doesn’t seem to matter your degree. You are now a nutrition expert.

Context Matters

It is difficult to compare food or diets without a specific context. For example, is low carb, high fat beneficial for your performance, it depends on a number of factors including the level of athlete you are and the duration and intensity of the event you are participating in. If you are a competitive marathon runner then a low carb, high fat diet is not going to help your performance, in fact it will probably hinder it. If you are a recreational ultra-endurance runner participating in an ultra-event with no expectations on time, then yes, the low carb, high fat diet could be for you.

Studying Nutrition is Bloody Hard

The most rigorous study design in scientific research is a double blind, randomised controlled trial, preferably one that contains a large sample size of participants. If we are wanting to investigate the specific health effects of a particular diet, let’s use the example of a low carb, high fat diet, then we would randomly assign a large group of people to a carefully controlled low carb, high fat diet and another group to a different diet i.e., a diet that follows the Australian Dietary Guidelines acceptable macronutrient distribution range (ADMR). We need to follow these two groups over a long period of time, tracking the specific health outcomes. A long time is not 12 weeks but at least 5+ years. Can you imagine being asked to change your diet and follow this way of eating, every day for 5+ years? Well, some researchers tried to do just that in one of the most expensive long term dietary intervention trials, The Women’s Health Initiative Randomised Controlled Dietary Modification Trial. Women were asked to follow either a low-fat diet (intervention diet) or a regular diet for several years. Guess what? Participants didn’t follow the specified intervention diet.


Adherence to a study diet is typically low particularly if for an extended period. There are several reasons why people eat, not only to live but for enjoyment, social and cultural reasons. In addition, consider the ethics of this study. Is it ethical to ask someone to change their diet for 5+ years, when we don’t know the long-term health effects? It’s just not practical to run these rigorous trials for many of the big nutrition questions. Short term randomised controlled trials are more feasible i.e., 3 months but these studies can’t measure the effects of dietary interventions over a long period of time and therefore inferences need to be made on the long-term effects.

As a result of the difficulties of carrying out randomised controlled trials, observational studies are prevalent. This type of study design involves observing the effect of a particular diet in individuals over a long period of time compared to individuals not following the diet and tracking health outcomes. There are difficulties with interpreting results from this type of study design as there are many confounders i.e., other factors that may affect the study outcome(s). This type of study design allows researchers to identify associations between variables, it does not allow cause-effect relationships to be determined.

Then there is the issue when we ask someone to follow a particular dietary pattern, let’s say low fat they are then replacing that fat with something else, maybe it’s carbohydrate or protein. Therefore, who is to say that the health effects we are measuring are because of fat or the other food/nutrient we just replaced the fat with.

Often dietary surveys are used in these types of studies such as food frequency questionnaires, in which the researcher is asking participants to report their dietary intake, prospectively or retrospectively, and this relies on both memory and accuracy of what they ate. This is flawed with errors. Furthermore, the nutritional composition of food differs, even from a similar vegetable or fruit. For example, a home-grown tomato can have a varied nutrient profile than a mass-produced tomato from the supermarket.

Environment & Individual Variation

Research tells you how on average a group of people responded to the intervention based on a particular environment, but it does not tell you how you, the individual will respond in an environment that changes constantly. Individuals respond physiologically differently to food and diet therefore what may be beneficial for one person may be completely different for another.

Commercial Motives & Marketing Claims from Industry

Like it or not, currently most nutrition research is funded by industry and underfunded by the government. Does this mean there is bias towards positive outcomes in industry funded research, it is highly likely. Identifying the source of funding for the research will help inform the reader whether there may be a conflict of interest. We also need to consider whether there are conflicts of interest declared by the researchers, do they have financial interest(s) to gain from the research and what is their research agenda.


Then there’s the supermarket aisles, full of food products with attractive and what can be misleading claims, “light”, “natural”, “low carb”, “low fat”, “cholesterol free” and “sugar free” and these can often be misinterpreted by the consumer. One of the main aims of food manufacturers is to get consumers to purchase their products, a sales tactic using carefully crafted language to attract the consumer.

So, how can you become a Sherlock Holmes and make yourself a little less confused about nutrition?

1. First, you need to own a bullshit detector. A bullshit detector requires critical thinking skills.

2. Some questions to ask yourself when next reading a nutrition piece or listening to someone provide nutrition advice are:

Is there a promist or a quick fix? Be critical of quick fixes. It is likely a doozy (aka nutritional misinformation), not sustainable or nutritionally sound. Check the science behind it, check the credentials of those making the claims.


Is it sensationalised information? Media information and social media influencers, intentionally or not, can oversimplify, cherry pick information and exaggerate the science, often confusing correlation for causation. Refer to point 3.

Is information based on personal stories or testimonials? Check the qualifications of the person providing the advice. What personal or financial gain do they have. Is there an evidence-based source for these claims.

Is the advice based on a single study? Refer to point 3. Evaluate the sample size, selection methods and data analysis.

What are the qualifications of the person providing the advice? Does this person have any qualifications for what they are talking or writing about?

Do you need to purchase products to follow the nutrition advice? Be very wary. Refer to the above points.

What is the context? Context matters, there is no black and white way, it depends on the situation.

3. Refer to systematic reviews for the highest level of evidence.

There will always be studies that have conflicting findings and therefore may provide differing opinions, so you need to consider all the available research. Systematic reviews summarise a particular research question by synthesising results of all existing primary studies related to each other, using strategies to minimise bias and random errors.

4. Determine who has funded the research, is it a government body or food industry, the former is likely to be more credible. For the latter you will need to be sceptical, use your critical thinking skills when interpreting the research.

5. Understand how to read food labels, check this link out to help you become a more critical label reader.

6. Think more broadly, not just about a particular nutrient but rather about dietary patterns. Our guest nutrition expert, Dr Tim Crowe explains the key dietary patterns for health here.

7. Remember not everyone responds the same to nutrition therefore there is no one size fits all nutrition approach.

8. If you are still confused and we don’t blame you, consider seeing a qualified nutrition professional for further advice.

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