Insulin Resistance and Metabolic Syndrome: Recognising Early Warning Signs Through an Integrative Pharmacological and Ayurvedic Perspective

India is currently home to more than 101 million individuals living with diabetes mellitus, according to the International Diabetes Federation (IDF) Diabetes Atlas, 11th edition¹. Type 2 diabetes mellitus rarely develops acutely; it is typically preceded, often by several years, by a largely unrecognised metabolic disturbance — insulin resistance — that is not routinely screened for in standard clinical checkups.

Patients presenting with fatigue, weight gain, elevated blood pressure, and dyslipidaemia are frequently managed as isolated conditions by different specialists. However, a substantial body of evidence suggests that these seemingly unrelated findings often share a single underlying root cause — insulin resistance — which is not being addressed at the primary healthcare level. This fragmented approach to management is compounded by the fact that insulin resistance itself produces no distinctive symptom of its own; it manifests only through its downstream consequences, each of which is conventionally treated as a separate diagnosis.

According to the Apollo Hospitals ‘Health of the Nation 2025’ report, based on screening of more than 2.5 million individuals across India, 26% were found to be hypertensive and 23% diabetic, and the majority of these individuals were asymptomatic². This represents a considerable population of undiagnosed at-risk individuals. Importantly, insulin resistance is reversible in its early stages, not necessarily through pharmacotherapy alone, but through appropriate dietary modification, targeted nutraceuticals, physical activity, and structured daily routines that support rather than burden metabolic function.

Within Ayurvedic medicine, this condition can be conceptually mapped to weak Agni (digestive fire) obstructed by Ama (residue of incomplete digestion). Classical Ayurvedic texts described this pattern of metabolic imbalance long before modern biochemical assays existed³. This review integrates a conventional pharmacological perspective with this Ayurvedic framework to provide a comprehensive, evidence-graded overview of insulin resistance, its molecular basis, warning signs, and management strategies, and situates these findings within the specific public health context of India.

The objectives of this review are threefold: first, to summarise the molecular and clinical pathophysiology of insulin resistance and its relationship to metabolic syndrome; second, to critically evaluate the evidence base for dietary, nutraceutical, Ayurvedic, pharmacological, and lifestyle interventions; and third, to examine the burden of insulin resistance-related conditions within the Indian population and the implications for primary care screening practice.

This topic carries particular relevance for undergraduate and graduate pharmacy education, since insulin resistance sits at the intersection of pharmacology, pharmacognosy, and clinical nutrition — three domains that are frequently taught separately but rarely integrated into a single clinical picture. Pharmacy professionals are often the most accessible healthcare contact for patients, particularly in Indian community pharmacy settings, and are therefore well positioned to recognise early warning signs, counsel on nutraceutical and lifestyle interventions, and refer patients for appropriate biochemical screening before overt diabetes develops. This review is written with that translational, practice-oriented purpose in mind, rather than as a purely academic exercise.

MATERIALS AND METHODS

This review is based on a narrative literature search conducted using PubMed and PubMed Central (PMC), with additional cross-referencing of Google Scholar for recent publications. Search terms included combinations of ‘insulin resistance’, ‘chronic low-grade inflammation and insulin resistance’, ‘IRS-1 PI3K Akt signalling’, ‘acanthosis nigricans and hyperinsulinaemia’, ‘metabolic syndrome diagnostic criteria’, ‘insulin resistance PCOS NAFLD’, ‘curcumin and GLUT4’, ‘cinnamon and glycaemic control’, ‘ashwagandha and cortisol’, ‘thiazolidinedione insulin resistance’, ‘ICMR-INDIAB’, and ‘Agni Ama Ayurveda metabolic syndrome’. Priority was given to peer-reviewed articles, systematic reviews, and meta-analyses where available, and nationally representative epidemiological data were used wherever possible to contextualise the Indian disease burden. For the Ayurvedic component, peer-reviewed Ayurvedic journal articles were preferentially cited over general health websites, in order to allow verifiability of claims.

This is not a systematic review in the strict methodological sense; no formal PRISMA-based screening with inclusion/exclusion criteria was applied. It is instead a narrative synthesis combining undergraduate pharmacology coursework with the Ayurvedic concept of Agni and Ama, supported throughout by literature evidence. Where the evidence base is strong (e.g., the exercise/GLUT4 mechanism), this is stated explicitly; where evidence is limited or conflicting (e.g., cinnamon supplementation), this is also stated transparently rather than presenting all claims with uniform certainty. Non-English language sources and unpublished/grey literature other than institutional reports (e.g., Apollo Hospitals, ICMR) were excluded.

RESULTS AND DISCUSSION

Pathophysiology of Insulin Resistance

Following carbohydrate ingestion, dietary starches are broken down into glucose, raising blood glucose levels. In response, the pancreas secretes insulin, which acts as a signalling ‘key’ that enables glucose transporters to move glucose from the bloodstream into cells for utilisation. In insulin resistance, target tissues — principally skeletal muscle, adipose tissue, and liver — become progressively less responsive to insulin signalling. Glucose uptake into cells is impaired despite adequate or elevated circulating insulin, and the pancreas compensates by secreting increasing amounts of insulin (hyperinsulinaemia). Over time, this compensatory mechanism places sustained stress on pancreatic beta cells, and in genetically or environmentally susceptible individuals, beta-cell function eventually declines, precipitating overt hyperglycaemia.

The physiological consequences are multifactorial: cells remain functionally ‘starved’ of glucose despite hyperglycaemia, contributing to persistent fatigue; chronically elevated blood glucose damages vascular endothelium, raising cardiovascular risk; unutilised glucose is diverted to hepatic lipogenesis and stored as visceral adiposity; and the liver, kidneys, and pancreas are subjected to sustained metabolic burden.

Chronic low-grade inflammation has been shown to play a central mechanistic role in this cascade⁴, a finding that maps conceptually onto the Ayurvedic description of Ama. Because each downstream consequence (dyslipidaemia, hypertension, obesity, and eventual type 2 diabetes) is frequently managed by a different specialist in isolation, the shared upstream driver of insulin resistance is often left unaddressed.

Molecular Mechanisms of Insulin Signalling Dysfunction

At the cellular level, insulin action is mediated through the insulin receptor (IR)–insulin receptor substrate (IRS)–phosphatidylinositol 3-kinase (PI3K)–protein kinase B (Akt) signalling cascade. Binding of insulin to its receptor activates receptor tyrosine kinase activity, leading to phosphorylation of IRS proteins, activation of PI3K, and downstream activation of Akt, which in turn promotes translocation of the GLUT4 glucose transporter to the cell membrane, enabling glucose uptake^5,6. In insulin resistance, this pathway is disrupted at multiple points: serine (rather than tyrosine) phosphorylation of IRS-1 impairs its interaction with PI3K, reducing downstream signalling efficiency⁵. This serine phosphorylation is promoted by several factors relevant to this review, including circulating pro-inflammatory cytokines (e.g., TNF-α, IL-6), excess free fatty acids and their lipid intermediates (diacylglycerols and ceramides), and activation of stress-related kinase pathways such as JNK and IKKβ/NF-κB⁵.

Adipose tissue plays a particularly central role in this process. Dysfunctional, hypertrophied adipocytes — as occur in visceral obesity — release increased quantities of adipokines, cytokines, and free fatty acids that impair insulin signalling in the liver, skeletal muscle, and pancreas⁵. Leptin, an adipocyte-derived hormone, illustrates this cross-talk: while leptin signalling normally supports glucose homeostasis via JAK2-mediated phosphorylation of IRS proteins, chronic hyperleptinaemia associated with obesity is linked to leptin resistance and impaired downstream insulin signalling⁵. Genetic factors also contribute; more than fifty mutations in the insulin receptor gene have been identified in association with rare, severe forms of insulin resistance, although such monogenic causes account for only a small minority of cases in the general population, with polygenic and acquired (lifestyle-related) factors predominating⁶. Understanding this molecular cascade is clinically relevant because it explains why interventions that reduce systemic inflammation (weight loss, exercise, certain nutraceuticals) and those that directly target the signalling pathway (thiazolidinediones, discussed later in this review) can each independently improve insulin sensitivity.

A further layer of complexity involves the progressive transition from compensated hyperinsulinaemia to overt beta-cell failure. In the early, compensated phase, pancreatic beta cells increase insulin output sufficiently to maintain normoglycaemia despite peripheral resistance; this phase may persist for years and corresponds to the period in which lifestyle intervention is most likely to achieve full reversal. Over time, however, sustained hypersecretion, combined with lipotoxic and glucotoxic stress on beta cells, leads to progressive beta-cell dysfunction and apoptosis, at which point insulin secretion becomes inadequate to compensate for peripheral resistance and overt hyperglycaemia emerges. This transition point represents a critical, and often irreversible, threshold, further reinforcing the clinical importance of identifying and intervening during the earlier compensated phase, when beta-cell reserve remains intact.

From Insulin Resistance to Metabolic Syndrome: Diagnostic Framework

The clustering of cardiometabolic risk factors around insulin resistance was first formally described by Reaven in 1988 under the term ‘Syndrome X’⁷. Since then, several expert bodies have proposed diagnostic criteria for metabolic syndrome, including the World Health Organization (1998), the National Cholesterol Education Program Adult Treatment Panel III (NCEP-ATP III, 2001), and the International Diabetes Federation (IDF, 2005)⁸. The IDF criteria require central obesity (ethnicity-specific waist circumference) as a mandatory component plus any two of: elevated triglycerides, reduced HDL-cholesterol, elevated blood pressure, or elevated fasting glucose. The NCEP-ATP III criteria instead require any three of five components (waist circumference, triglycerides, HDL-cholesterol, blood pressure, fasting glucose) without treating central obesity as mandatory. These differing definitions can yield meaningfully different prevalence estimates in the same population, and this variability is a recognised limitation when interpreting epidemiological data on metabolic syndrome⁸. For clinical and educational purposes, however, the underlying message across all criteria is consistent: metabolic syndrome represents a cluster of interrelated abnormalities driven substantially by insulin resistance, rather than a set of unrelated diagnoses.

Table 1: Comparison of Major Diagnostic Criteria for Metabolic Syndrome

As illustrated in Table 1, the WHO criteria are unique in mandating direct evidence of insulin resistance or diabetes, whereas the NCEP-ATP III and IDF criteria rely on surrogate clinical markers. This distinction is clinically relevant: an individual may meet NCEP-ATP III or IDF criteria for metabolic syndrome based on blood pressure, lipid, and waist circumference thresholds alone, without any biochemical confirmation of insulin resistance itself. This further supports the argument made throughout this review that fasting insulin and HOMA-IR testing, although not part of any standard metabolic syndrome definition, provide mechanistically more direct information than the surrogate criteria in routine use.

Public Health Burden and Screening in India

The Indian Council of Medical Research–India Diabetes (ICMR-INDIAB) study, a nationally representative cross-sectional survey of more than 113,000 individuals across 31 states and union territories, reported an overall weighted prevalence of diabetes of 11.4%, prediabetes of 15.3%, hypertension of 35.5%, generalised obesity of 28.6%, abdominal obesity of 39.5%, and dyslipidaemia of 81.2%⁹. Notably, all of these metabolic non-communicable disease indicators except prediabetes were more frequent in urban than rural areas, and considerable inter-state variation was observed, with diabetes prevalence ranging several-fold between states of differing socioeconomic development⁹. These findings collectively indicate that India is undergoing a substantial and geographically uneven metabolic disease transition.

From a health systems perspective, this scale of burden cannot be addressed through diabetes diagnosis alone; it necessitates earlier intervention at the insulin resistance stage. India's National Programme for Prevention and Control of Non-Communicable Diseases and the Ayushman Bharat Health and Wellness Centre network represent existing infrastructure through which population-level screening for hypertension and diabetes is being scaled up; however, routine screening protocols at these facilities remain centred on fasting glucose and blood pressure rather than insulin resistance-specific markers such as fasting insulin or HOMA-IR. Incorporating even opportunistic screening for early warning signs described in this review, particularly in individuals with a family history of diabetes, central obesity, or acanthosis nigricans, could meaningfully improve early detection at low additional cost within this existing infrastructure.

Natural History and Progression

The progression of insulin resistance to overt metabolic disease is variable between individuals but broadly follows a recognisable pattern. In the earliest years, resistance builds with minimal or no visible symptoms. Over three to five years, fatigue, weight gain, sugar cravings, and mildly elevated blood pressure typically emerge. Between five and ten years, a full metabolic syndrome phenotype often develops, frequently accompanied by multiple diagnoses and medications. Beyond ten years, serious complications such as elevated cardiovascular event risk and renal impairment may occur. Because this progression can remain clinically silent for a prolonged period, early identification substantially improves the likelihood of reversal.

Early Clinical Warning Signs and Screening Markers

The presence of three or more of the following features warrants targeted biochemical testing:

• Persistent fatigue, including tiredness despite adequate sleep, reflecting impaired cellular glucose uptake
• Afternoon sugar cravings, associated with relative intracellular glucose deficiency despite hyperglycaemia
• Central (abdominal) weight gain, reflecting hepatic conversion of unutilised glucose to visceral fat
• Difficulty concentrating (‘brain fog’)
• Acanthosis nigricans — dark, velvety hyperpigmented skin patches at the neck, axillae, or elbows — a recognised clinical marker of hyperinsulinaemia¹⁰
• Blood pressure above 130/80 mmHg
• Dyslipidaemia (elevated LDL-cholesterol and/or triglycerides, reduced HDL-cholesterol)
• Nocturnal urinary frequency
• Delayed wound healing
• Hair thinning or hormonal irregularities, frequently observed in association with PCOS

Recommended screening investigations include Fasting Blood Glucose (normal <100 mg/dL; prediabetic 100–125 mg/dL; diabetic ≥126 mg/dL), Fasting Insulin (normal <12 µIU/mL — not routinely ordered but clinically informative), HbA1c (normal <5.7%; diabetic ≥6.5%), and the HOMA-IR index, calculated as (Fasting Glucose × Fasting Insulin) ÷ 405, with values below 1.0 considered normal. Of these, fasting insulin and HOMA-IR are the most sensitive for detecting insulin resistance prior to the development of overt dysglycaemia, yet they remain the least frequently ordered in routine primary care.

Table 2: Recommended Biochemical Screening Panel for Insulin Resistance

Table 2 summarises the recommended screening panel discussed in this review. In primary care settings where fasting insulin assays may not be readily available or affordable, HbA1c combined with a lipid profile and waist circumference measurement can serve as a reasonable interim screening approach, with referral for fasting insulin/HOMA-IR testing reserved for individuals meeting three or more of the clinical warning signs described earlier in this review.

Role of Obesity and Adipose Tissue Dysfunction

Obesity, and in particular visceral adiposity, is among the strongest acquired risk factors for insulin resistance. Expanding adipose tissue in obesity becomes hypoxic and infiltrated by pro-inflammatory macrophages, shifting adipokine secretion toward a pro-inflammatory profile (increased leptin, resistin, and inflammatory cytokines; decreased adiponectin), and increasing circulating free fatty acid flux to the liver and muscle⁵. This adipose tissue dysfunction is now understood to be a primary driver linking obesity to insulin resistance, rather than excess fat mass alone; individuals with metabolically ‘healthy’ obesity and preserved adipose tissue function show comparatively less insulin resistance than those with visceral fat accumulation and adipose tissue inflammation, even at similar body mass index. This distinction has practical relevance for this review’s emphasis on waist circumference and central obesity, rather than body weight alone, as a more clinically meaningful screening parameter.

Downstream Complications: Dyslipidaemia, Hypertension, NAFLD, and PCOS

The metabolic consequences of sustained insulin resistance extend across multiple organ systems. Hepatic conversion of excess glucose to triglycerides contributes to dyslipidaemia; renal sodium retention and vascular stress contribute to hypertension; and impaired beta-cell reserve over time culminates in type 2 diabetes mellitus. Collectively, these abnormalities increase the risk of cardiovascular disease, stroke, and chronic kidney disease. From a pharmacy practice perspective, this clustering has a practical implication: a patient presenting with a new prescription for an antihypertensive or a statin, without a documented diabetes diagnosis, may still be an appropriate candidate for insulin resistance screening, since dyslipidaemia and hypertension frequently precede the biochemical diagnosis of diabetes by several years.

Insulin resistance is also increasingly recognised as a central pathophysiological driver of non-alcoholic fatty liver disease (NAFLD), promoting hepatic lipid accumulation, inflammation, and fibrosis¹¹. In women, insulin resistance is closely linked with polycystic ovary syndrome (PCOS), a common endocrine disorder affecting an estimated 6–20% of women of reproductive age¹². Hyperinsulinaemia in PCOS contributes to hyperandrogenism and ovulatory dysfunction, and the two conditions — PCOS and NAFLD — frequently coexist, sharing insulin resistance, obesity, and chronic low-grade inflammation as common upstream drivers^11,12. This overlap illustrates why insulin resistance is best understood as a unifying metabolic disturbance rather than a series of isolated organ-specific conditions, and reinforces the rationale for screening young women presenting with menstrual irregularity or hirsutism for insulin resistance rather than treating reproductive symptoms in isolation.

Ayurvedic Perspective: Agni and Ama

Within Ayurveda, Agni refers not to literal fire but to the body’s digestive and metabolic capacity. Strong Agni is associated with efficient digestion and stable energy metabolism, whereas weak Agni is associated with sluggish digestion, impaired metabolism, and eventual weight gain and fatigue³. The proposed mechanistic sequence by which weak Agni contributes to insulin resistance can be summarised in five stages: (i) weak Agni develops secondary to poor dietary habits, irregular eating patterns, chronic stress, or excess Kapha; (ii) digestion becomes incomplete; (iii) this generates Ama, a sticky residue of undigested material, conceptually analogous to inflammatory by-products or reactive metabolic intermediates in modern physiology; (iv) Ama is proposed to obstruct cellular signalling pathways; and (v) cells consequently become less responsive to insulin.

A useful conceptual analogy is that insulin functions as a traffic signal operating correctly, but if the road itself (Ama) is obstructed, glucose (traffic) still cannot move efficiently. Conventional pharmacological management largely addresses the signalling mechanism, whereas the Ayurvedic approach emphasises clearing the underlying obstruction before allowing normal metabolic flow to resume. Dosha imbalance is also implicated: Kapha imbalance is associated with sluggish metabolism and weight gain, while Pitta imbalance is associated with inflammation and hepatic stress; classical texts describe both as contributing jointly to this condition. It is worth noting that this Agni–Ama framework, while conceptually compelling and consistent with the inflammatory basis of insulin resistance described in modern literature, has not itself been subjected to controlled clinical validation as a diagnostic construct, and should be regarded as a complementary explanatory model rather than a replacement for biochemical diagnosis.

From a pedagogical standpoint, presenting the Agni–Ama model alongside the IRS-1/PI3K/Akt signalling pathway described earlier in this review offers pharmacy students a useful bridge between two knowledge systems that are typically taught in isolation. Both frameworks converge on a broadly similar conclusion — that a chronic, low-grade disruptive process (inflammatory mediators in modern physiology; Ama in Ayurveda) progressively impairs an otherwise intact signalling mechanism (the insulin receptor cascade; Agni) — even though the underlying vocabulary, historical origin, and degree of experimental validation differ substantially between the two systems. Recognising this conceptual parallel, without overstating the degree of formal equivalence between them, may help students and practitioners communicate metabolic health concepts to patients using culturally familiar language, particularly in Indian primary care settings where Ayurvedic concepts remain widely understood even among patients who do not otherwise use Ayurvedic treatment.

Dietary and Nutraceutical Interventions

Ayurvedic tradition treats food as a therapeutic tool rather than merely a caloric input. The following dietary interventions are traditionally used to support insulin sensitivity, with corresponding modern evidence critically appraised below.

Beyond individual foods, overall dietary pattern and meal composition are increasingly recognised as independently important to insulin sensitivity, a consideration particularly relevant to the traditional Indian diet. Meals with a high proportion of refined carbohydrate consumed in isolation (for example, white rice or refined-flour products without accompanying protein, fibre, or fat) produce a sharper postprandial glucose excursion than the same carbohydrate consumed alongside dal, vegetables, and a source of healthy fat, because protein, fibre, and fat all slow gastric emptying and blunt the glycaemic response. This principle, sometimes described as ‘food order’ or ‘meal sequencing’ in contemporary nutrition literature, aligns closely with the traditional Indian thali format of combining grain, lentil, vegetable, and fat in a single meal, and offers a practical, culturally familiar counselling point that does not require patients to adopt an unfamiliar dietary pattern.

Bitter gourd (Momordica charantia, Karela) is among the most extensively studied. It contains charantin and polypeptide-p, compounds implicated in enhanced cellular glucose uptake and improved insulin sensitivity in laboratory and preliminary clinical studies, although most large-scale reviews conclude that standardised human trials remain necessary before definitive claims can be made¹³. Fenugreek (Trigonella foenum-graecum, Methi) contains 4-hydroxyisoleucine, and several clinical trials report improved glucose tolerance with regular consumption. Neem leaves are traditionally used for their bitter, Ama-clearing action, while spinach provides magnesium, a cofactor relevant to insulin signalling pathways.

Among whole grains, millet (bajra) and barley offer a comparatively lower glycaemic index and beta-glucan fibre content that slows glucose absorption, while moong dal provides easily digestible plant protein without sharply elevating postprandial glucose.

Turmeric (Curcuma longa, Haldi) has comparatively strong laboratory-level evidence: curcumin has been shown in cell and animal studies to upregulate GLUT4 transporter activity and improve insulin sensitivity in muscle tissue¹⁴, although robust human trial data remain limited. Co-administration with black pepper (piperine) is traditionally recommended to enhance curcumin bioavailability.

Cinnamon (Cinnamomum verum, Dalchini) evidence is genuinely mixed and warrants honest appraisal, in contrast to how it is frequently presented in popular literature as a guaranteed intervention. Some meta-analyses report a modest reduction in fasting blood glucose with cinnamon supplementation¹⁵, while other well-controlled trials report no significant effect¹⁶. This discrepancy likely reflects variation in cinnamon species, dose, and duration across studies. Cinnamon appears reasonably safe at typical culinary doses but should not be presented as a guaranteed therapeutic intervention.

Foods best avoided or minimised include refined white rice and maida-based products, sugar-sweetened beverages, repeatedly reheated cooking oils, processed and fried foods, excess dietary salt, and alcohol, all of which are associated with increased Ama formation and impaired digestive efficiency within the Ayurvedic framework, and with adverse glycaemic and lipid profiles within conventional nutrition science.

Table 3: Summary of Evidence Strength for Dietary and Nutraceutical Interventions