The metabolic and biological impacts of food insecurity

A study, albeit from the USA, found that women experiencing FIS were characterised by greater variability in temporal patterns of eating both within and between days, lower consumption of fibre and protein and higher consumption of carbohydrates compared with food secure women^{(Reference Nettle and Bateson15)}. Amongst these patterns, the one most strongly associated with FIS was a variable time gap between eating occasions, such as when breakfast is typically eaten. In a comparison of low-income UK adults (income below the UK median of £30 800 and not in full-time education), mean daily energy intake and inter-day variations in energy intake were similar regardless of whether individuals were classified as food secure or insecure which may suggest differences in eating patterns between the UK and USA^{(Reference Shinwell, Bateson and Nettle16)}. People who are food insecure have increased odds of living with overweight or obesity, with the most marked differences seen in adult women from high-income countries who have 50 % increased odds of obesity compared with women who are food secure^{(Reference Nettle, Andrews and Bateson17)}. This is sometimes called the ‘food insecurity-obesity paradox,’ but the phenomenon is less pronounced in men and children generally, or in women from low/middle-income countries^{(Reference Nettle, Andrews and Bateson17)}. There is also evidence from some countries, such as Canada, that individuals experiencing FIS eat more highly processed foods^{(Reference Dicken, Qamar and Batterham18)}.

Even after correcting for income and socio-economic status, people living with FIS have 40–70 % increased odds of obesity and an increased chance of developing metabolic syndrome^{(Reference Park and Strauss19)} as well as some non-communicable diseases^{(Reference Salinas-Roca, Rubió-Piqué and Carrillo-Álvarez20)}. This suggests that these enhanced risks are unlikely to be linked solely to poverty. Furthermore, FIS is associated with accelerated biological ageing estimated using telomere length^{(Reference Hastings, Shalev and Belsky21)}. As expected, given these findings, a greater all-cause mortality is observed in populations with FIS beginning at an OR of 1·28 (CI = 1·08, 1·52) in those who are marginally food insecure rising to an OR of 2·60 (CI = 2·17, 3·12) in those with severe FIS^{(Reference Gundersen, Tarasuk and Cheng22)}. Data from animal models (such as starlings^{(Reference Andrews, Zuidersma and Verhulst23)} or rats^{(Reference Myers, Majewski and Schaefer24)}) and human randomised controlled trials^{(Reference Alhussain, Macdonald and Taylor25–Reference Farshchi, Taylor and Macdonald27)} strongly suggest that health and obesity associations with FIS are causal. Potential reasons may include irregular eating patterns and anticipated food scarcity leading to increases in body weight or disrupted energy balance, and preferences for energy dense foods favouring weight gain^{(Reference Folwarczny, Christensen and Li28)}. Research in starlings subjected to FIS found shorter telomere length and inhibited feather regrowth, indicating reduced investment in somatic maintenance and repair^{(Reference Andrews, Zuidersma and Verhulst23)}. Variable or unpredictable food intake is sufficient to cause weight gain in the absence of changes to diet quality or total energy intake^{(Reference Andrews, Zuidersma and Verhulst23)}. Therefore, it is hypothesised that FIS directly triggers reductions in energy expenditure or more efficient energy bioavailability from food. The biological mechanisms underlying this effect are unclear but may include a stress response to irregular food supply which impacts hunger, appetite and preference for energy dense foods; an adverse impact of fasting on dietary thermogenesis or voluntary energy expenditure; or an inability to develop the anticipatory hormonal responses to meals requisite for homeostatic control of blood glucose and fats, for example normal insulin release. It is also plausible that changes to the gut microbiota may be implicated in the altered metabolic response to FIS. The gut microbiome supports the extraction of energy and nutrients from foods, produces multiple metabolites with relevance to health, supporting normal immunity and protection of the host against pathogens^{(Reference Lawley and Walker29)}. However, the gut microbiota is dependent upon a steady supply of substrate for its maintenance, with non-digestible carbohydrates a major substrate^{(Reference Ruxton, Kajita and Rocca30)}.

Although each person has a unique microbiome signature, it is known that the composition and activities of the microbiota can change in response to diet, medication, stress and illness^{(Reference Ruxton, Kajita and Rocca30)}. The microbiome can therefore be altered in response to irregular eating patterns and poor-quality diets, which may, in turn, increase the risk of chronic disease, for example bowel cancer, inflammatory bowel disease, diabetes or allergy^{(Reference Round and Mazmanian31)}. In contrast, higher fibre diets promote more beneficial species (particularly lactic acid bacteria) and their metabolites (particularly short-chain fatty acids) within the gut, which may lower disease and allergy risks^{(Reference Duncan, Conti and Ricci32)}. However, whilst certain disease states are associated with reduced bacterial diversity and altered metabolic profiles in observational studies, there is a paucity of cause-and-effect data from well-conducted longitudinal studies and clinical trials. A barrier to this is the innate variation in the gut microbiome that makes identifying specific and reproducible disease signatures challenging^{(Reference Walker and Hoyles33)}.

Literature on the relationship between FIS and the microbiome remains sparse, although differences in faecal metabolite profiles between food secure and insecure USA students have been noted^{(Reference Mohr, Jasbi and Vander Wyst34)}. Underlying mechanisms to explain these could include the impact of lower fibre, nutrient-poor diets on the gut microbiota, as well as stress and environmental factors. Emerging research from animal studies^{(Reference Devkota, Wang and Musch35–Reference Chassaing, Koren and Goodrich37)} suggests negative effects of some of these components on the gut microbiota, glucose tolerance, inflammation and opportunistic pathogen expansion, although findings still need to be verified in humans.

As mentioned previously, lower fibre intakes are more common in populations experiencing FIS^{(Reference Nettle and Bateson15)}. A lack of fibre may have long-term health impacts for individuals since the breakdown of fibre by gut bacteria can promote gut mucosa integrity through various actions including (a) the utilisation of bacterial metabolites such as short-chain fatty acids; (b) more rapid gut transit which reduces colonic exposure to putrefactive microbiota fermentation products; (c) release of polyphenol compounds from plant fibres; and (d) microbial synthesis of nutrients including vitamin K, folate and riboflavin.

FIS, behaviour change and the care pathway

Obesity affects more than 60 % of the UK adult population but is more common in populations experiencing FIS^{(Reference Park and Strauss19)}. Prevention strategies do not appear to have been successful given the UK’s static and high incidence of obesity. In the NHS in England, adult weight management is currently delivered via a tiered system. Individuals move between tiers depending on the intensity of intervention required, often needing to complete a lower tier to access a higher Tier (e.g. Tier 2 for referral to Tier 3) (Figure 1).

Figure 1.

Weight management tiers in adult clinical settings (NICE, 2025; ref⁽³⁹⁾).

Tier 1 interventions include public health campaigns, adverts, websites and brief interventions in primary care. Brief interventions in primary care can be effective as demonstrated in the BWeL trial^{(Reference Aveyard, Lewis and Tearne38)}.

Tier 2 is aimed at individuals with a BMI ≥ 30 kg/m². Interventions include group interventions and the prescription of Orlistat, a lipase inhibitor.

Tier 3 involves more specialist one-to-one interventions, using multidisciplinary teams and typically in a hospital setting. It is aimed at individuals with severe or complex obesity (BMI ≥ 40 kg/m² or ≥ 35 kg/m² with obesity related co-morbidities). Within this tier, options include very low-calorie diets or the prescription of glucagon-like peptide-1 receptor agonists, such as Semaglutide or Liraglutide⁽³⁹⁾.

Tier 4 includes bariatric (metabolic) surgery, but individuals are required to receive input from tier 3 multidisciplinary teams before being referred for this (typically 12 months)^{(Reference Hazlehurst, Logue and Parretti40)}.

Although the recent approvals by NICE for new pharmacotherapies, such as Liraglutide⁽⁴¹⁾ and Semaglutide⁽⁴²⁾, may improve options for the treatment of obesity, other barriers exist to effective clinical management of obesity. These include a patchy provision of tier 3 service⁽⁴³⁾ and a lack of GP confidence and training to initiate conversations about patients’ weight^{(Reference Tremblett, Webb and Ziebland44)}. From the patient perspective, misunderstanding or fear of stigmatisation can hamper engagement with health services⁽⁴⁵⁾. One study reported that people take, on average, nine years to approach their GP about their weight^{(Reference Hughes, Ahern and Kasetty46)}. Therefore, people living with FIS who may be at a high risk of obesity may face difficulty seeking and receiving help to manage their obesity.

Understanding and supporting behaviour change: Lower socio-economic status is associated with a higher BMI^{(Reference Robinson, Jones and Marty47)}. This relationship appears to be mediated by health motives, i.e. how much participants ‘bought into’ healthy eating and concerns about body weight, but not by executive functioning (i.e. an individual’s capacity for planning ahead and monitoring their own behaviour). In the UK, FIS in adults was indirectly associated with higher BMI via greater psychological distress and ‘eating to cope’^{(Reference Keenan, Christiansen and Hardman48)}. Whilst the Theory of Planned Behaviour is a useful framework to study how beliefs, attitudes, perceived identity control and subjective norms influence behaviour^{(Reference Schifter and Ajzen49)}, it is more useful to change health behaviour rather than simply observe it.

The Behaviour Change Wheel provides a conceptual framework^{(Reference Michie, van Stralen and West50)} to analyse behavioural drivers with three layers of drivers likely to influence behaviour. These are (i) individual sources of behaviour e.g., social, physical, psychological (ii) interventions such as education, coercion, incentivisation and (iii) policy options including guidelines, fiscal measures and service provision. As developed by the Behavioural Change Wheel, successful interventions focus on the COM-B dimensions, which are Capability, Opportunity and Motivation leading to Behavioural change^{(Reference Michie, van Stralen and West50)}. In the context of healthier diet, ‘capability’ reflects an individual’s psychological or physical ability to choose healthier diets; ‘opportunity’ refers to the food environment including enablers and barriers within this and ‘motivation’ encompasses reflective and automatic mechanisms which either activate or inhibit behaviour.

Qualitative research has examined current barriers to healthier diets in adults at risk of FIS. Poor mental health, financial stress and high food prices were barriers to change, while current food choice was influenced by social factors (e.g., child food preferences) and environmental factors (e.g., temptations in local food shops)^{(Reference van der Velde, Schuilenburg and Thrivikraman51)}. Parents living with FIS commented that they bought treat foods or takeaways because this was affordable and made their children happy. Often healthy eating knowledge is overridden by desire or pressure for convenience, poor cooking facilities, time pressure, stress and desire to avoid conflict at mealtimes. Population and policy interventions could help to address some of these barriers to healthier eating and may involve planning, legislation, regulation and fiscal measures (Table 3).

Table 3.

Policy opportunities to influence food choice in populations with FIS

FIS, food insecurity; FSA, Food Standards Agency.

Behavioural change techniques tested in weight management interventions suggest goal-setting approaches are effective. For example, a meta-analysis of thirty-five interventions found that the most effective interventions were based at home or in community settings^{(Reference Bull, McCleary and Li61)}. As noted in this study, healthy eating, self-monitoring, delivery through personal contact and targeting multiple behaviours further increased effectiveness. Intervention designs are increasingly using co-production, where target communities, such as people experiencing FIS, are actively involved in the development of behavioural interventions. Effective co-production, according to authors who developed a children’s health strategy, is guided by nine principles built on the values of equality, reciprocity and agency^{(Reference Albert, Islam and Haklay62)}.

Co-production is underpinning a new study – the CHarMINg project – to develop interventions to support multiple behaviour change⁽⁶³⁾. So far, early insight has been gained into the misalignment between target community and intervention developers’ goals, resulting in improved training and supportive conversations about behaviour change. Figure 2 summarises three steps that could be considered when working with groups experiencing FIS to instigate more supportive, client-centred conversations about health⁽⁶³⁾.

Figure 2.

Key steps to delivering client-centred conversations about health.

Achieving policy change

It is said that ‘what surrounds us, shapes us’. Within Western food environments, there is an abundance of food and drink that is high in energy, saturated fat, free sugars and salt. Foods high in saturated fat, salt and free sugars are heavily advertised, marketed and promoted, encouraging consumers to buy more, or to make unplanned purchases⁽⁶⁴⁾. In practice, this has a disproportionately negative impact on lower income families, compounding inequalities in health and household budgets. Regulating the food environment is an equitable way of improving health. Evidence from Scotland suggests that discretionary foods account for 20 % of total daily energy and half of daily sugar intake⁽⁶⁵⁾. Discretionary items (confectionery, cakes, biscuits, pastries, savoury snacks, sugar-sweetened beverages and alcoholic drinks) tend to be high in calories, low in nutritional value and are unnecessary for health. Mean daily intakes of discretionary foods do not appear to differ by deprivation score, but there are significant differences in the consumption of sugar-sweetened beverages (113 g in most deprived v. 59 g per day in least deprived) providing 9 g v. 3 g in daily intakes of free sugars, respectively⁽⁶⁶⁾. Cost is just one of the factors influencing food choice in lower income groups with transportation, energy costs and cooking/storage facilities also being important. FIS is greater in single parent and single adult households,⁽⁵⁾ which are more likely to be impacted by food costs, particularly those in lower socio-economic groups or with disabilities and long-term health conditions⁽⁶⁷⁾. Furthermore, 34 % of people blamed the cost of living situation for their diets being less healthy, while 45 % said they were deprioritising healthy eating.

Addressing barriers within the food environment is a more equitable way of improving population diets than relying on individual change: examples include reformulation⁽⁶⁸⁾, restricting promotion of foods/drinks high in fat sugar and salt⁽⁶⁹⁾, nutrition guidance for the out-of-home sector and a code of practice for children’s menus⁽⁷⁰⁾. Food Standards Scotland is supporting and building on this work, as outlined in its new public health nutrition strategy⁽⁷¹⁾ and the Eat Well Your Way online resource⁽⁷²⁾. Future policy work will need to support sustainability goals, such as meat and dairy reduction⁽⁷³⁾, while considering the cost barriers experienced by lower income consumers.

Policy sits in a context of political, economic, sociological, technological, legal and environmental considerations that influence strategic organisations. Civil servants follow UK Government’s Green book⁽⁷⁴⁾ that outlines the ROAMEF policy development cycle: this takes decision-makers through the Rationale, Objectives, Appraisal (of different options), Monitoring (of implementation), Evaluation (of outcomes) and, finally, the Feedback⁽⁷⁴⁾. Good policymaking sets benefit against potential detriment, impact on inequalities, unintended consequences, cost/benefit, return for investment and opportunity costs. Successful policy depends on evidence, politics and delivery coming together. UK nutrition policy – with the Scientific Advisory Committee on Nutrition at its core – follows the key steps of identifying a need to evaluate and review risks (Figure 3). The process of evidence gathering and consultation leading to policy change is not usually a quick outcome. One example is the folic acid fortification policy,⁽⁷⁵⁾ which began in 1991 with the identification of a need (prevention of neural tube defects in infants), moved onto appraisal of policy options in 2001 but has, since then, seen ongoing cycles of requests for evidence, scrutiny and consultation. Indeed, despite agreement for mandatory fortification of non-wholemeal flour with folic acid in September 2021, at time of submission of this paper (summer 2024) policy still had not been implemented.

Figure 3.

How nutrition research fits into the policy cycle.

Regarding FIS, good policy depends on clear articulation of the issue with firm definitions; for example, ‘sufficient food’, ‘nutritious food’, ‘normal growth’ and ‘food preferences’ remain difficult to quantify and open to interpretation. If FIS is defined as lacking ‘nutritious food’, as proposed by several organisations, then most people in the UK are in this category since very few meet current dietary recommendations. Another challenge is the lack of consistency in dietary messaging especially the proliferation of ‘healthy, sustainable diets’ endorsed by expert bodies, such as Eat-Lancet, One Blue Dot, Mediterranean diet, which could create confusion since they add complexity to the basic principles defined by the Eatwell Guide. It is often assumed that eating a healthy diet is more expensive than the current average diet, but this is not necessarily the case^{(Reference Scarborough, Kaur and Cobiac76)}. A whole systems approach to dietary recommendations with cross-government co-operation could be beneficial as this would help resolve current tensions between sustainability, nutrition and affordability.