Insulin Resistance: Warning Signs and Foods That Help Control Blood Sugar Levels

Insulin resistance can develop gradually, without obvious signs, and when the body no longer responds properly to this hormone, blood sugar levels can rise, leading to prediabetes and, subsequently, type 2 diabetes. Corina Pelin, a registered dietitian, explained to Digi24.ro the main risk factors and the changes that can help improve insulin sensitivity. Specialists emphasise that diet, physical activity, sleep, and stress all influence this mechanism.

What insulin resistance is

Under normal circumstances, insulin helps glucose from the blood enter cells to produce energy. When cells become less sensitive to insulin, glucose has greater difficulty entering and accumulates in the bloodstream. The pancreas responds by producing more insulin, which can lead to hyperinsulinaemia. If this compensatory mechanism fails, blood sugar levels rise, and over time prediabetes and type 2 diabetes may develop. Elevated insulin levels also promote energy storage and the accumulation of abdominal fat, which can contribute to the onset of fatty liver disease. People with insulin resistance may find it difficult to lose weight and tend to gain it quickly.

Signs that may indicate a problem

• Accumulation of fat around the abdominal area
• Frequent cravings for sweets or carbohydrates
• Fatigue and drowsiness, particularly after meals
• Rapid weight gain and difficulty losing weight

In android-type obesity, fat is deposited predominantly on the abdomen, whilst the arms and legs remain relatively slim — this is visceral fat, surrounding the organs, which is associated with a high metabolic risk. An abdominal circumference of over 80 cm in women and 94 cm in men can be a relevant indicator. Family history also plays a role: people with a parent or grandparent who had diabetes are at greater risk of glucose metabolism disorders.

Tests that can detect insulin resistance

The HOMA-IR index is calculated by multiplying fasting blood glucose by fasting insulin and dividing the result by 405 (when blood glucose is expressed in mg/dL); a value around the threshold of 2 may raise suspicion of insulin resistance. Insulin levels can also provide clues: in the early stages, blood glucose may be normal, yet insulin levels already elevated (hyperinsulinaemia). The oral glucose tolerance test (OGTT) involves measuring blood glucose and insulin before and after the administration of glucose.

Associated long-term risks

Insulin resistance is linked to metabolic syndrome and can contribute to type 2 diabetes, obesity, cardiovascular disease, and fatty liver disease. In women of childbearing age, it is also associated with polycystic ovary syndrome. Ongoing research is exploring its connection with Alzheimer's disease, certain types of cancer, depression, and changes in immune response.

Prediabetes corresponds to a fasting blood glucose level between 100 and 125 mg/dL, or a glycated haemoglobin (HbA1c) level between 5.7% and 6.4%. Diabetes is diagnosed at an HbA1c of 6.5% or above, or a fasting blood glucose of 126 mg/dL or above, confirmed according to medical criteria. Unlike type 2 diabetes — which is linked to insulin resistance, genetic predisposition, excess weight, and lifestyle — type 1 diabetes is an autoimmune condition in which the immune system destroys the insulin-producing beta cells of the pancreas, requiring the administration of external insulin.

Factors that promote insulin resistance

These include a sedentary lifestyle, an unbalanced diet, insufficient sleep, and chronic stress, as well as the accumulation of fat within muscle cells (the lipotoxicity theory). A high intake of saturated fats — from butter, animal products, coconut oil, and palm oil — can promote this phenomenon and reduce muscle sensitivity to insulin. A lack of physical activity reduces the ability of muscles to use glucose from the blood, whilst regular exercise increases insulin sensitivity. Insufficient sleep and elevated cortisol levels, caused by chronic stress, can in turn affect blood sugar regulation.

How it can be improved

A balanced diet, regular exercise, adequate sleep, and effective stress management can improve insulin sensitivity and, over time, reduce resistance to this hormone. Physical activity is essential, as muscles consume glucose from the blood, including after meals. Through consistently maintained healthy habits, insulin resistance can be significantly reduced or even reversed in certain cases.

Foods that support insulin sensitivity

Plant-based foods rich in fibre play an important role. Fibre helps regulate blood sugar levels, promotes a feeling of satiety, and supports bowel function. An intake of approximately 30–35 grams of fibre per day is a useful target for most adults.

Soluble fibre — found in oats, legumes, apples, chia seeds, and psyllium — forms a gel that slows the absorption of glucose and can reduce post-meal blood sugar spikes. Other fibres increase stool bulk and support transit, whilst fermentable fibres and resistant starch feed the beneficial bacteria in the microbiome. Resistant starch is found, for example, in less ripe bananas and in potatoes or grains that have been cooked and then cooled.

Good sources of fibre include beans, lentils, chickpeas, soya, vegetables, whole fruits, wholegrains, nuts, and seeds. Fruit is best consumed whole rather than as juice, since juicing removes some of the fibre and speeds up the absorption of sugars. Fibre also helps remove excess cholesterol and supports the health of the gut microbiome.