Why do some autistic people eat a restricted diet?

What’s the difference between a biscuit and an apple? This may sound like a simple question – however, the seemingly obvious answer can tell us a lot about why some autistic people struggle considerably with eating particular foods, but can tolerate or enjoy others. Many autistic people have what we call sensory processing differences – that is, differences with how they experience smell, texture, taste and sight (amongst other senses), compared to people who aren’t autistic. In the case of food, autistic people can be hypersensitive (very sensitive) or hyposensitive (undersensitive) to the way the food looks, smells, tastes and feels. If an autistic child is hypersensitive to taste, for example, they would likely prefer food that is very plain; if they are undersensitive to taste, they may seek out strong flavours or spicy food. Many autistic people will have specific preferences about their food and may eat what others see as a restricted diet. This often consists of food that may be considered plain and predictable in terms of the way it tastes, smells and looks, as well as its texture. Examples of such foods include biscuits, crisps, crackers, chicken nuggets, chips, plain pasta and bread.

This takes us back to the question of the biscuit and the apple. While biscuits usually have a predictable texture, taste, consistency and tend to always look the same, especially if buying one particular brand, apples (or any other fruit or vegetable) can vary considerably in size, taste, consistency and texture. When we eat a biscuit, we generally know what to expect every time, so the element of surprise is very limited. On the other hand, apples can taste and look different, and might even vary in texture and firmness. This lack of consistency can be overwhelming and overstimulating for some autistic people, who may only be able to eat a small selection of plain foods with predictable textures and consistent tastes and smells.

As many of those foods may fall into the category of processed foods, parents of autistic children can be subtly blamed or openly stigmatised for not providing their children with a healthy diet, sufficient choice of foods, or for not ‘encouraging’ them enough to try a more varied diet. However, the reality is much more complicated than that. One ‘side effect’ of food that has been mass-manufactured for efficiency – this includes many types of processed foods – is consistency. In other words, foods like biscuits, chicken nuggets, crackers and crisps tend to look, taste and smell identical every time. The same can’t be said about fruits and vegetables, or freshly prepared, cooked food. From that perspective, it makes sense that many of the foods that are tolerable for autistic people with sensory processing needs will be processed foods – they are, by definition, consistent and predictable in terms of their texture and the way they look, taste and smell.

What is ARFID?

Some autistic people experience particularly significant difficulties around food that could come under the diagnostic label of Avoidant and Restrictive Food Intake Disorder (ARFID). ARFID is a relatively new diagnosis, first added to the American Psychiatric Association’s Diagnostic and Statistical Manual in 2013. It’s important to note that ARFID isn’t diagnosed exclusively in autistic people, however the two can often co-occur.

Some of ARFID’s characteristics are:

• low appetite or general disinterest in food
• avoidance of eating because of sensory processing differences
• weight loss
• nutritional deficiencies
• significant psycho-social implications – for example, the child might be unable to eat in the same room as the rest of their family or in the dinner hall at school because they find the smell of the food overwhelming
• a need for nutritional supplements or tube-feeding.

Children with ARFID may have a strong aversion to new food and anxiety around even seemingly slight variations to the food’s smell, texture or the way it looks. This often means that they may have a preference for a specific brand, and any changes to the packaging or the recipe may result in the food no longer being seen as safe.

While ARFID may be a relatively new diagnosis, this does not necessarily mean that autistic children experiencing significant difficulties around food is a new phenomenon. It’s likely that before these patterns were formally recognised – and to an extent even today – the very real distress experienced by some autistic children could have been attributed to being ‘fussy’ or a ‘picky eater’ or similarly judgemental remarks that fail to consider the root causes of the issue and the real distress it results in.

While there is still a lot we don’t know about the relationship between autism and eating difficulties, we need to be mindful of and avoid simplistic explanations that imply the autistic child is in some way defiantly resisting trying new food – this would be inaccurate and simplistic. We need to recognise that this is likely to be a profoundly distressing experience for them on a sensory level, and one that requires careful support planning.