Sub-theme: Medical issues.

A number of participants described having medical problems which affected their eating, typically through motivating them to avoid certain foods or environments. The most common of these were food allergies, leading participants to avoid specific foods. Similarly, one participant who experienced migraines described avoiding certain foods to avoid triggering the condition. Two participants experienced gastrointestinal problems, which again led them to alter their diets by eliminating certain foods, or eating more of foods with a beneficial effect. A further two participants had difficulties with physical coordination, which led them to avoid communal eating environments due to difficulty using cutlery, or fear of social embarrassment. One participant felt that their mental health conditions and associated medication led them to eat less due to stomach discomfort, and one participant avoided communal, loud eating environments due to medical hearing problems making the experience unpleasant.

Sub-theme: Sensitivity.

Participants described avoiding certain foods, or in one case seeking out specific foods, in order to manage their sensory input. For some, this was avoiding certain foods due to hypersensitivities to aspects like taste, texture, smell, and temperature. While some participants described this in terms of dislikes- “if the texture is off, that food can be just fantastic and I'll still loathe it” (Participant 4), for others this sensitivity was so extreme it caused pain, gagging, or a “meltdown” (Participant 9). While most participants described aversion to specific sensory experiences, such as certain textures, one participant actively used food to increase their sensory stimulation by actively seeking out strong flavours.

Hypersensitivity to certain sensory stimuli also motivated participants to avoid or alter their eating environments. A common experience was avoiding loud environments due to hypersensitivity to noise, which often led to participants avoiding communal eating areas such as restaurants or school dining halls:

“I’d rather not eat in a loud restaurant or dining hall, or just anywhere where I can’t talk to people next to me or just have some peace and quiet… if I’m in an environment where there’s lots of background noise, I find it hard to filter out the background noise. And I think, because I’ve always been good at music, I’m very sensitive to variations in sound” (Participant 2).

These environmental sensitivities meant that participants required a degree of control around their eating environments. Where this kind of control was not available, this sometimes led to avoiding eating in that environment completely:

“I don’t like the smell sometimes that forks and knives have on them. So I will insist on clean cutlery, and if it smells peculiar I will send it back and get clean ones. And in fact sometimes mugs out of the dishwasher have that smell in them as well, and I don’t know what that smell is but it’s pungent. And so if it doesn’t smell just right I won’t eat out of it or on it” (Participant 5).

Participants additionally felt that their eating behaviours were influenced by a difficulty in identifying internal sensations, or interoception- specifically, problems identifying if they were hungry or full. This was viewed by one participant as being closely related to stress levels, and was felt to contribute to under-eating- “it’s the immediate feeling of being full. You know, two bites and you’re full, that’s it. Even if you were a bit hungry, two bites and you’re done” (Participant 3).

Sub-theme: Executive functioning.

Difficulties with executive functioning also impacted some participants’ eating habits. Problems with aspects such as planning and memory made it difficult to acquire food, with participants describing issues with food shopping, cooking and food preparation, and ordering food. At worst, this led to not eating at all:

“Planning and doing things in the right order can be a big barrier to accessing food. for example, I don't leave my room unless I have a visual mental plan of exactly what I'm going to get, where it is, and how I'm going to get it (often with a backup plan or two so that I don't panic if my first plan is disturbed), and if I don't come up with a satisfactory plan I just don't go at all. Doing things in the right order can be difficult if anything isn't according to plan, like if I drop something or someone tries to talk to me—it's as if once I start executing a plan I enter a sort of autopilot mode, and the system gets lost if it's bumped off course. Oftentimes when that happens I quickly give up and pick something at random to get out as quickly as possible, and that can result in accidentally picking something sensory-bad” (Participant 9).

Consequently, accessing food was viewed by some as requiring a large amount of mental energy and preparation. When participants were distracted or preoccupied by other things, such as stress, this limited the amount of mental energy they could devote to food and eating, again leading to not eating. This appeared to be linked to difficulties with interoception, or having the executive capacity to mentally register the sensation of hunger: “literally forgetting to eat because I just get too busy to, I don’t know, recognise the signals” (Participant 3).

Sub-theme: Rigidity and routines.

As well as avoiding certain foods, another key behaviour described by participants was that of eating similar foods repeatedly (described by Participant 10 as “samefooding”), or forming a specific routine around eating. This appeared to be related to the mental tendency towards rigidity and routines associated with autism: “you’re quite rigid, you’re quite kind of control orientated, you’re quite kind of perfectionist” (Participant 10).

For a number of participants, food was viewed as a key aspect of life that they could control. This led to repetitive and routine-based eating habits, including a preference for familiar foods and an aversion to trying new things. However, the importance of these routines varied across participants: some described their routines as a preference which could be broken without distress, whereas others were more rigid in their behaviours. For one participant, this rigidity was in part motivated by a fixation on information and numbers. They described finding comfort in their BMI always being at the exact centre of the “healthy” spectrum, and always reading food labels: “I think I’m in control of everything simply because I’m in control of the facts, and I know exactly why I’m doing what I’m doing” (Participant 3).

Rigid thinking patterns also contributed towards eating habits, in particular categorical thinking styles creating aversions towards certain foods. Several participants described having one bad experience with a specific food- for example it causing food poisoning- and not eating that food again: “The milk was sour at school once, and I wouldn’t drink milk for a long time after” (Participant 7). For a small number of participants, this rigidity manifested as a compulsion towards meal completion, regardless of hunger. Alternatively, other participants felt their rigid thinking styles led them to restrict or avoid food. Trying to break these routines or rigid thought patterns was seen as requiring mental effort, “[It is] easier if I don’t have to think about something new to eat. If I know something is good, and that, you know, I’ll feel ok after eating it, then I’m likely to eat it again” (Participant 8).

Sub-theme: Social.

Participants identified their behaviours around food as impacting how they behaved in social situations involving eating. This was particularly pronounced around communal eating spaces: firstly, an aversion to certain environments—such as the noise associated with communal spaces like restaurants- prevented or made participants reluctant to attend social events in these locations. Difficulties around eating in communal spaces was related to participants’ abilities to manage their routines and preferences around food, which was made more difficult in social situations. Eating with other people meant that they could not control or avoid experiences or behaviours that they found aversive: for example, if they found overeating distasteful they could not prevent other people overeating, leading to feelings of awkwardness or isolation:

“How do people eat like that? I don’t get it. But I don’t want to eat like that so you know, I don’t feel inspired. I feel a bit repulsed actually, just sit back and observe in grotesque curiosity I suppose” (Participant 3).

Similarly, eating with other people meant that individuals could not always control or select the food being eaten, particularly in the case of family meals eaten at home. Where the food was not palatable or was particularly sensory aversive, participants described eating separately to their family.

As well as being highly aware and sensitive to the behaviours of people around them, some participants were concerned that the people around them would be similarly aware of their own behaviours. These described feeling self-conscious or embarrassed around their own eating habits or difficulties in front of others, leading them to eat alone or only with close acquaintances. For one participant, this aversion to eating in social situations was related to viewing eating food as a purely functional requirement, rather than a pleasurable experience:

“When given the choice, I always prefer to eat alone rather than with people. Eating is not about "hanging out", it's about "putting food in my belly so it stops complaining". There's an element of social anxiety to that, what if I spill food on my shirt… I am self-conscious about the things I am because they're things I would be self-conscious about if someone did them around me” (Participant 4).

However, the majority of other participants described still finding enjoyment in eating with other people. Participants generally described preferring, and enjoying, eating with smaller social groups in quieter settings, and so did not experience avoiding busier social environments such as restaurants as a problem.

Sub-theme: Weight and eating disorders.

Only 2 participants in the sample reported having a BMI in the defined “normal” weight range: all other participants were classified as being in either the under- (n = 4) or the overweight/obese (n = 6) range. All participants with a BMI in the underweight range either had a current ED diagnosis, or a history of EDs. The overweight participants did not identify their weight as a problem: only one participant, who had previously been overweight but lost weight, saw being overweight as a significant problem in their life. Apart from this participant and individuals with diagnosed EDs, no other participant felt that their eating behaviours caused any physical or health problems.

Both individuals in both the under- and overweight ranges exhibited similar underlying behaviours, but with different effects. For example, both groups described experiencing rigidity around their eating. For those who were underweight this rigidity appeared to contribute towards restriction, or eating only low calorie foods, leading to weight loss. For those who were overweight, this rigidity and repetitiveness tended to be focused around high calorie foods, leading to weight gain:

“I think that sometimes I find that I’ve gotten into a rut with the same thing over and over, and if its something like- something high calorie like chocolate for instance, I struggled with that. Because I started eating it at a certain time of day and then I kept doing that for a long time and I was gaining weight and I noticed that I was constipated and I had to stop that habit. But it’s very easy for me to get into a habit” (Participant 8).

Similarly, both groups described rigid thinking styles that alternatively contributed to under- or overeating. For some, previous experiences had led them to develop a strong compulsion towards completing meals, eating quickly, or over-eating, which they now found difficult to break. Where participants were exposed to certain behaviours or models around eating or body image around childhood, they found these persisted into adulthood and were difficult to break:

“If you’re not taught how to eat well, and you know the sort of behaviours you see as a child is emotional comfort eating, I guarantee you that’s what my mum does. Then that’s the sort of thing you’re exposed to, you know, having a bowl of cereal sized for six people before you go to bed sort of thing, or you know, asking for a bowl of ice cream and you get the entire tub before you go to bed, just because somebody’s upset you you eat a candy bar. You know, that sort of thing, if that’s what you’ve been exposed to, which I was, then that, the sort of patterns that you assume” (Participant 3).

This participant further suggested that the rigid thinking styles associated with autism may make autistic people particularly vulnerable to these kind of environmental influences, especially in childhood:

“We’re all so literal, and all these messages that are out there and all these skinny girls on Instagram- now it’s the bodybuilders on Instagram, you know, the fitness freaks on Instagram… I think these things are all around us, I think we’ve got to think about them very clearly and carefully. Particularly when we’re thinking about how literal autistic people take these messages” (Participant 3).

These experiences therefore led to the formation of certain attitudes or behaviours around food which, combined with the rigidity associated with autism, proved difficult to challenge. For some individuals, this led to under- or overeating, to the degree that their body weight was classified medically as unhealthy, or the development of EDs:

“Autistic people often misuse “black and white thinking”, and I know that affects what and when I eat at home, because if I go to get a snack and my mom says it's too sugary or it's saved for something/someone else, I don't get a different snack, I just don't eat. I think that sort of thing contributed to my eating disorder at the start” (Participant 9).

Across the sample, the participants who identified autism as having the biggest impact on their eating were typically those diagnosed with EDs, although the aspects of autism they felt influenced their eating (such as rigidity) were highly similar to those without EDs. Out of the 12 participants interviewed, 6 reported having experienced an ED in their lifetime: 4 participants had experienced AN, 1 had been treated for BN, and 1 was undergoing treatment for BED. The motivating behaviours underlying their symptoms were highly similar, and strongly overlap, with those seen with those contributing to under- and overeating, and subsequent weight loss or gain. For example, the participant with BED identified a strong compulsive element to their eating leading to overeating:

“I definitely have a tendency towards completion that will cause me to finish a meal that I am not necessarily hungry to finish, and that may be one thing about it. There’s definitely a compulsive element to my eating a lot of times. I also think that, you know, there’s an impulsive element to my eating, and they both sort of come together to, you know, create binge episodes when they do occur” (Participant 1).

Notably, participants with EDs did not typically describe their ED symptoms in terms of emotions, or as strongly influenced by body image. Rather, they strongly related their EDs to the impact of autism, including the role of thinking styles, or viewed it in a functional manner- for example, fulfilling their need for control. The participant with BED explicitly stated that they did not experience the negative emotions around food traditionally associated with binging: rather than binging to cope with negative emotions, they instead found their binging was impulsive and triggered by having access to food (Participant 1).

Sub-theme: Progression from childhood.

Participants generally described becoming more flexible around food as they became older, with one participant suggesting that their eating became more adventurous with “maturity and self-reflection” (Participant 1). Whilst some participants viewed this as happening gradually, without necessarily requiring conscious effort, others described this as an active process:

“For a long time I would eat only foods I recognized. I worked pretty hard to overcome that… and I have learned to like the experience of trying a new thing, even if it may not be what I know… they've improved because I worked at them” (Participant 4).

Specific changes included making an effort to try new foods, and therefore gradually reducing the associated anxiety associated with unfamiliar foods. Some participants felt that their eating improved from childhood due to support from their family in this process: one participant described how their parents used routines to help introduce new foods in a boundaried, safe way:

“I was raised with a rule that if we ate out at a buffet I had to pick one food I'd never tried before, before I was allowed to eat whatever else I wanted; and if we ate at home, I had to eat everything that was given to me (I literally spent hours sitting with my dinner, especially if it was squash or asparagus) but I was allowed to ask for a "no-thank-you portion," which is smaller. So I feel like that habit helped me diversify my tastes and it definitely gave me courage to try new things” (Participant 9).

By contrast, one participant felt that taking control of their own eating, separate to the habits they had been raised with as part of their family, was key to improving their eating habits and their attitude towards food. For this participant, self-education as an adult around diet and nutrition was key to this process:

“I think not knowing that my body weight was actually linked to how much I put down my neck- no one ever told me that the two were linked together- was just a big issue as well. So I think this has been a lifelong thing for me. Never knowing that the two were related, never knowing it was something that I had at least some degree of control, responsibility for. As a responsible adult. I think once I discovered that about five or six years ago and once I discovered that it was something that I could change and I did have some power over, then that was empowering in itself and that’s when I started to take some control over it” (Participant 3).

Sub-theme: Coping as an adult.

Participants commonly described one of the key ways they coped with the influence of autism on their eating as an adult as simply avoiding problem areas, and finding ways to cope around any potential difficulties. For example, one participant who ate a vegan diet due to their self-identified special interest in the environment and animals was careful to take food supplements and eat a balanced diet to ensure they received the necessary nutrition. Similarly, individuals who struggled to eat in restaurants would avoid these kind of locations, and where unavoidable would find ways to ameliorate this difficulty: for example, by asking their partner to order their food for them.

One key area of difficulty which participants described finding ways to adapt around was that of cooking. Cooking was commonly described as a difficult task, either due to executive functioning difficulties or due to sensory aversion to touching or preparing certain foods. Some participants described managing this by predominantly eating in preferred restaurants (where restaurants were not an environmental aversion), or by eating pre-prepared meals. Others used only familiar recipes which represented less of an executive functioning burden. Individuals with families described difficulties cooking as they sometimes were unable to eat the same meal as the rest of their family. One participant managed this by cooking all meals at the weekend, enabling them and their family to individually choose from a selection of meals during the week. Significantly, in the case of cooking and meal planning for the week, participants described using their tendency towards routine-based behaviour as a strength: they found that planning meals ahead of time helped both with cooking and eating, “making meal plans helps, I think, because I then kind of have to—I don’t get into a panic about “oh, what should I eat”. I’ve kind of got it all sorted out before” (Participant 11).

Sub-theme: Support from others.

Participants also described support from family and friends as vital in managing their eating. This included having food prepared for them in a specific way, being encouraged to try new things, and being reminded to eat. Crucially, support was seen as most helpful where it respected their boundaries:

“They also know about my "nope" reflex. Some things just make me go "nope" and they don't chase me with them or ask me to try them anyway… We all abide by these boundaries and it helps tremendously” (Participant 3).

Sub-theme: Medical professionals.

The only participants who had ever discussed their eating with a medical professional were those who had sought treatment for EDs. Of those who sought treatment, they found the experience most beneficial when the impact of their autism on their eating was acknowledged, considered and respected: “My experiences, be they atypical, are still perceived as valid” (Participant 1). However, participants felt that this required a knowledge of autism and its potential influence on eating that medical professionals may not have:

“I think it would be helpful if more professionals were aware of the sensory differences and the frequently-comorbid gastrointestinal issues that can make eating difficult for people with autism, as well as the samefooding phenomenon and other routines. Also, in general, they need to understand that meltdowns and sensory overload aren't tantrums or bad behaviour and can't be helped by treating them as such—especially with food, it's not as simple as being picky, it can range from unpleasant to uncomfortable to painful” (Participant 9).

Participants both with and without EDs strongly felt that medical professionals needed to view the influence of autism on their eating as intrinsic, rather than as a choice. They also emphasised that their eating should not be unnecessarily pathologized or seen as an illness:

“I think that would be the biggest thing I would want medical professionals to know, not necessarily for myself but for my youngest daughter. To know that there is a category of people who have these eating issues and they don’t actually have anything to do with the shape of their body. And to tell them that they need to change is wrong. It’s ethically wrong and it’s going to ethically fail, it’s going to cause these people more damage. It’s not the best way to go about things” (Participant 3).

Where the individual was experiencing eating problems, participants felt that the best way to approach this would be using flexibility, and having knowledge of the difficulties commonly associated with autism and eating, whilst retaining awareness that different people will have different experiences.