The AspireAssist could be the most intuitive weight-loss therapy ever proposed. It works as a feeding tube in reverse: with the aid of an endoscope and a tiny blade, a physician places an internal catheter into the stomach and pulls it out through the skin. Shortly thereafter, the patient wakes up and goes home with a circular plastic window into the belly. For the next several months, about 20 minutes after every meal, the patient affixes an external drain to this implanted skin-port and spills a good bit of his or her gastric contents directly into the toilet.

This intervention is the latest in a series of minimally invasive devices approved by the United States Food and Drug Administration (FDA) for the treatment of obesity. Its proponents cite data: there is no argument that ‘aspiration therapy’ helps people lose weight. Its detractors cite their revulsion: many argue that if one wanted to surgically induce an eating disorder, this would be the way. The tenor of grievances raised by both professional and lay observers has ranged from eye-rolling snark to complete outrage. For the bluntness of its method, this novel treatment strategy has struck numerous onlookers as ugly, reckless and dangerously transgressive.

These objections speak to a fundamental misunderstanding of obesity as a biological process. Indeed, the vocal anxiety over what constitutes morally acceptable intervention lays bare tacit and stubborn assumptions about weight as a reflection of character. The AspireAssist highlights an ongoing tension between two duelling narratives: obesity as a multifactorial epidemic, and obesity as a failure of will. A conscious acceptance of the former often masks a knee-jerk adherence to the latter, leaving the issue, at its roots, unresolved.

The steady rise in overweight and obese individuals on a global scale has been particularly noticeable since the mid-20th century, and a few sweeping cultural forces can help to explain it. The stage was likely set by industrialisation, which facilitated sedentary lifestyles and a progressive abundance of calorie-rich nourishment. More specific sociopolitical factors, such as income disparities, agricultural investment priorities and the recent ubiquity of highly processed foods, have also been scrutinised as drivers of obesity’s regional variation. These forces are pitted against metabolic tendencies that evolved over millennia in a very different milieu – that is, one of relative scarcity, where one ate when one could. In recent years, research into human physiology has provided a wealth of new insight about this system’s intricacy, variability and vulnerability.

The emerging science of weight gain has supported ‘the medicalisation of obesity’ – its configuration as a disease that should be addressed by healthcare providers in clinical spaces. This concept in turn has led to the development of a whole suite of dedicated obesity therapies over and above the conventional recommendation of diet and exercise. Multiple prescription medications are currently approved for weight loss. Bariatric surgery, in which parts of the stomach and small intestine are cut out and rearranged, dates back decades; it has become increasingly common thanks to improvements in technique and outcomes over time.

In an already crowded field of weight-loss therapies, however, there are no magic bullets: diets and drugs yield dividends that are often modest and temporary, while surgical intervention is relatively expensive and can bring complications. Thus, a spate of novel alternatives, more aggressive than dieting but less invasive than surgery, have emerged. These include devices that occupy space inside the stomach, creating a sense of fullness; bypass sleeves that physically separate food from the intestinal tissue that would otherwise absorb; and, of course, the AspireAssist. All are predicated on the same understanding of obesity as a mechanistic problem worthy of a mechanistic fix.

In this era of medicalised obesity, however, a quiet moral calculus about weight management still operates in the background. Being overweight is stigmatised despite its rising prevalence. Even when the pounds are successfully shed, the method of doing so is itself subject to judgments of personal virtue. Social science research, for instance, shows that patients who lose weight through bariatric surgery are viewed as lazier and less competent than those who lose weight through diet and exercise alone. Because the AspireAssist seems to work through an even more rudimentary approach, it has ushered these lingering prejudices into the light and provides a valuable opportunity to interrogate them explicitly.

Aesthetic objections to the AspirAssist have been raised on a fairly general basis, as reflected by the number of headlines that describe it as ‘disgusting’. Use of the AspireAssist trespasses the body’s natural boundaries, revealing its private workings rather unceremoniously to the world. The mental image of chyme – the half-digested slurry of our meals as they enter the bowels – can be as viscerally unpleasant as that of emesis or faeces. Yet the artificial exposure of stomach contents seems to be uniquely bothersome to others in the context of this intervention, this condition.

Enfolded within these expressions of physical disgust is a less explicit but no less intense element of moral disgust. Commentary by the late-night talk show host Stephen Colbert serves as a noteworthy illustration. ‘Many patients are enjoying their chest-mounted barf-bots so much,’ Colbert quipped about the device, ‘they say they want to keep it forever.’ The bit works by doubling down on audience revulsion: characterising caloric intake as fundamentally a joyful act casts obesity in the light of grotesque self-indulgence.

For other critics, a treatment approach designed around the deliberate expulsion of food is tantamount to ‘medically sanctioned bulimia’. The AspireAssist has become, to my knowledge, the only FDA-approved bariatric intervention that has merited trigger warnings in online discussions. The device’s mode of action has been deemed injurious enough to warrant shielding eating-disorder patients and survivors from the stress of its very description. Conflating bulimia and obesity, however, diminishes the independent gravity of both. This criticism implicitly frames weight gain as an eating disorder in its own right, and constitutes a radical misapprehension of how obesity arises and why it endures.

Research on the biological underpinnings of obesity continues to proliferate at a fever pitch. The fact that we are still asking elementary questions about disease pathogenesis despite this volume of data attests to the difficulty of the problem. To reduce this multifactorial reality down to a behavioural weakness of temperament is inevitably to render it a cartoon.

When I started medical school in 2007, I learned about body mass in terms of easy thermodynamics: weight change equals caloric intake minus caloric expenditure. Contemporary research, however, pays increasing attention to the many different mediators of obesity onset, taking for granted the fact that energy consumption and extraction differ widely from one individual to another. Against concerns that the AspireAssist will diminish the importance of personal responsibility in obesity management, it is worth considering the many predisposing factors that exist outside the realm of personal control.

The variables at play fall into two major categories: ‘homeostatic’ and ‘hedonic’. Homeostatic risk factors pertain to metabolic physiology – in other words, the various means by which the body maintains itself. These risk factors are being identified at almost every level of biological organisation. Large, genome-wide surveys have isolated several genes that might predispose some to weight gain. Animal studies have suggested that certain nutritional exposures during development can impact how genes are expressed early in life and, by consequence, how calories are later stored. At the level of our internal organs, evidence suggests that obese individuals might have specific abnormalities in the movement of their guts – a tendency for delayed emptying of the stomach into the small intestine, for example. Risk might also be contingent on the microbiome and interactions between organisms within the bowel; at least one case report documented rapid and unexpected weight gain in a woman following faecal transplantation therapy from an overweight stool donor.

Hedonic variables, on the other hand, comprise environmental stimuli such as stress levels and food palatability, as well as psychological risk factors such as mood, body image and health beliefs. While hedonic influences can have a potent effect on weight gain, an honest assessment must also recognise their deep interplay with the physiological realm. Stress, for example, has the ability to affect gene expression.

The device removes 30 per cent of each meal: this apparent lack of therapeutic subtlety invites unsubtle ways of thinking about obesity

At the intersection of the homeostatic and hedonic are two especially relevant states: hunger (an impulse to eat) and satiety (the sense of fullness). Current research describes these states as the products of an elaborate neurochemical mechanism, one tuned through conditioned learning over the early years of life but also regulated by a host of fluctuating and measurable hormones. Thus, while it might be seductive to separate homeostatic and hedonic obesity subtypes, in reality, these two risk categories are often intertwined.

The AspireAssist has a way of destabilising our appreciation of all this complexity. The device, which removes approximately 30 per cent of the caloric density of each meal, seems to operate at the same rudimentary level of thermodynamic arithmetic that I encountered early in medical school. This apparent lack of therapeutic subtlety invites a return to unsubtle ways of thinking about obesity itself.

Certain critics worry, for example, that the AspireAssist does not do enough to change behaviour. Providing an artificial outlet for food without neutralising its gustatory rewards, they argue, could never be effective as a long-term weight-loss strategy. A recent brief on aspiration therapy in The BMJ invokes apocryphal stories from the last years of the Roman Empire, when decadence was supposedly so widespread that deliberate vomiting became a commonplace technique for enabling continued eating. To the degree that this reference dovetails with a longstanding, reductive view of obesity, the AspireAssist pours fuel on the fire.

The device’s investigators have been sensitive to these critiques, though their data-based response is often overlooked. A recent pilot study found that no binge-eating habits developed over the course of the trial. In fact, there was reason to believe that positive behavioural modifications had occurred. Careful evaluations of the calories contained in both test meals and gastric aspirates found that drainage of food from the stomach accounted for only 80 per cent of the weight loss observed. As a result, the study team speculated that the device had encouraged slower chewing, greater water intake, and more structured meal schedules, all leading to additional caloric restriction.

Larger studies on safety and effectiveness are still pending, but so far the device appears competitive with other minimally invasive bariatric interventions. On a patient-by-patient basis, the AspireAssist helps far more than it harms. For many bystanders, the visual image of aspiration therapy remains inexcusably offensive. Yet as we come to understand the many ways in which the deck is stacked against obese individuals, we should become more open to therapies that work.

More generally, the value of an expanding suite of obesity therapeutics is tied to the fact that certain patients will respond uniquely well to certain interventions. Particular combinations and intensities of homeostatic and hedonic risk factors will vary, such that what looks on the surface like a single disease likely represents many different pathways toward a shared physical manifestation. The biological route that any given patient follows to arrive at obesity yields in turn a uniquely specific set of therapeutic targets, which might include, for example, neurohormonal dysfunction in one patient, microbial imbalance in another, and mood disorder in a third.

This concept aligns with our growing emphasis on personalised medicine, which optimises treatments by tailoring them to the individual. It provides an especially compelling framework for thinking about weight-loss therapy, suggesting that approved interventions, alone or in combination, might come to be deployed in an increasingly precise way.

This model necessarily includes the AspireAssist, however crude its mode of action might seem. Before prescribing aspiration therapy, practitioners must screen rigorously for binge-eating tendencies, excluding vulnerable candidates from the use of this device. At the same time, the fact that obesity and disordered eating can overlap by no means implies that they always do. The co-occurrence of these two processes in a minority of cases does not eliminate the device’s potential benefit in the substantial remainder.

The device seems to sidestep the punitive processes we’ve come to expect when transitioning toward a healthier weight

The AspireAssist is just one of many minimally invasive obesity therapies under recent or active development. The FDA recently approved two designs for distensible balloons that reside in the stomach for months at a time in order to curb caloric intake. Specialised sleeves have been designed for implantation in the small intestine, inhibiting the tissue’s absorption of nutrients as they pass through. An electrical stimulator called the Maestro can be surgically implanted to deliver periodic shocks to the vagus nerve, a direct conduit between the gut and the brain (how these shocks mitigate obesity is somewhat unclear, but the working assumption suggests an interference with hunger signalling). At certain medical centres, stomach tissue is being deliberately destroyed as a means of reducing absorption.

Much like the AspireAssist, these interventions represent mechanical constraints on digestive physiology. Judging by the volume of popular commentary, though, these other interventions pose relatively little challenge to our aesthetic or moral sensibilities. By contrast, aspiration therapy transforms the act of eating into a matter of overt plumbing. Among the alternatives mentioned here, it is the only one to reside partially outside the body; it is the only one to require regular manual manipulation, making treatment a particularly visible and active process.

In concept, aspiration therapy confronts us with weight-loss therapy as an act of ongoing physical violation. It disrupts the obese body, but somehow in the wrong way – amending the body without taxing the brain. We wonder: where is the nausea, the sweat, the sacrifice? Where are the hard limits, and where is the pain that pushes up against them? An externalised device such as the AspireAssist seems to sidestep the punitive processes that we’ve come to expect of patients transitioning toward a healthier weight.

Reasonable constraints do exist within the AspireAssist’s design, though they are not immediately on display. The device comes installed with a counter mechanism that allows 115 aspiration events before needing to be reset in close follow-up with a clinician. The supervised use of this intervention facilitates, in the long-term, a subtle restructuring of thought and behaviour, a gentle adjustment in metabolic and motivational set points. The pilot study’s lead author, Shelby Sullivan, has suggested that visibility might itself be one of the device’s therapeutic properties; seeing one’s partially digested meals on their way out of the body, she notes, likely compels more regular reflection on dietary decision-making.

Admittedly, this more generous interpretation of the AspireAssist is exactly the message that its manufacturers are hoping to advance. It is built into the device’s diplomatic branding – ‘assistance’ emphasising its role as a facilitator rather than a shortcut to weight loss; ‘aspiration’ playing on a dual meaning of forward striving and outward drainage. More cynical critics of the intervention have noted that its patent holder, Dean Kamen, is also responsible for the Segway brand of electric scooters, a comparison that appears to have two basic aims. First, it calls attention to the AspireAssist’s commercial motivation, challenging its therapeutic potential by defining it as a product of market forces. Second, it attempts to equate both technologies as enablers of idleness, designed to avoid the need for physical work.

Neither argument strikes me as particularly compelling. The ripe financial incentives of bariatric medicine, which should be obvious to even the most casual observers, have been and will be responsible for much of the field’s ongoing innovation. Mechanical weight-loss interventions are now in abundance, all directed at the large number of patients for whom dedicated lifestyle measures have proven insufficient. Grading these therapeutic options according to their perceived virtue lends credence to an obsolete value system that misses the point entirely.

If the AspireAssist continues to offend for the progressive boldness of its artifice, we might do well to remember everything that is artificial about the contemporary obesity epidemic and the cultural milieu in which it has arisen. An earnest commitment to wellness entails an openness to effective therapies that might seem ill-fitting at first glance.