What is insulin?
Insulin is a hormone which is produced by the β (beta) cells of the pancreatic islets (a region of the pancreas). The hormone is responsible for the regulation of glucose in the bloodstream.
In response to high levels of glucose in the blood, the β-cells (which are sensitive to blood glucose) release insulin, resulting in the absorption of glucose into the liver, fat, and skeletal muscle cells. Upon absorption, the glucose is converted into glycogen (a short-term storage form of glucose), fat (a longer-term energy storage) or used to generate energy within the cell. The result is the level of glucose in the blood stream decreases back to a ‘normal’ level.
What is insulin resistance?
Insulin resistance (IR) is defined as the ‘impaired ability of insulin action’, with a principal effect being a decrease in the glucose lowering ability of the hormone.
Where IR occurs in the cells of the skeletal muscles and fat cells (peripheral IR), the cells are unable to absorb circulating glucose. IR occurring in cells of the liver (hepatic IR), a decrease in glycogen synthesis and storage occurs, along with a reduced suppression of a process called gluconeogenesis (the generation of glucose), meaning more glucose is generated and released into the bloodstream. The results of both peripheral and hepatic IR are a prolonged elevation in blood sugar, (a condition called hyperglycaemia) and a decreased uptake of circulating triglyceride and an increased breakdown of fat stores.
What are the consequences of insulin resistance?
IR is most often linked to the development of type 2 diabetes mellitus (T2DM), a condition characterised by an inability to regulate blood glucose levels despite adequate levels of insulin, resulting in an increase demand for insulin, resulting in early β-cells failure and declining insulin levels over time.
The mechanism of IR on the development of T2DM is not completely understood, but it is known that IR results in the blood glucose levels remaining elevated for longer. The consequence is that more insulin is released from the β-cells due to the prolonged glucose presence, which overtime results in an accumulation of deposits of a protein (Amylin), disrupting the structure and function of the β-cells and therefore insulin production.
In addition to T2DM, the development of non-alcoholic fatty liver disease (NAFLD) is also associated with IR, although whether the development of NAFLD is the cause or result of IR is not fully understand. Evidence does show IR is likely to increase the risk of NAFLD. This is proposed due to the known effects of IR, causing the influx of fat (specifically free fatty acids) into the liver and IR being associated with rapid weight gain, obesity, high blood pressure, elevated blood lipids (fats), sleep apnoea, inflammation, increased sedentary behaviour and intake of excessive dietary fat, all of which contribute to the development of NAFLD.
What are the causes of insulin resistance?
There are several risk factors associated with the development of IR, including ethnicity and a genetic predisposition. A modifiable risk factor found in many with IR is being overweight or obese, particularly if excess weight is carried around the stomach (known as abdominal obesity).
To review whether your weight increases your risk, you can calculate your body mass index (BMI) using the formula below: (NHS BMI calculator)
BMI = Weight (kg) / (Height (m) * Height (m))
Then compare your results (considering your ethnic heritage) against the tables below:
|All ethnicities (except: Asian, |
|Low Risk||Increased Risk||High Risk|
|18.5 – 24.9 kg / m2||25 – 29.9 kg / m2||>30 kg/m2|
|Asian; Black-African; |
|Low Risk||Increased Risk||High Risk|
|18.5 – 22.9 kg / m2||23 – 27.4 kg / m2||>27.5 kg/m2|
To determine your risk from abdominal obesity, you can measure your waist as shown below and compare the results to the tables:
|White European / Black African / Middle Eastern / Mixed Origin|
|Low Risk||High Risk||Very High Risk|
|Men||<94cm (37″)||94 – 102cm (37 – 40″)||>102cm (40″)|
|Women||<80cm (31.5″)||80 – 88cm (31.5 – 34.6″)||>88cm (34.6″)|
|African Caribbean / South Asian / Chinese & |
|Low Risk||N/A||Very High Risk|
|Men||<90cm (35.4″)||N/A||>90cm (35.4″)|
|Women||<80cm (31.5″)||N/A||>88cm (31.5″)|
How can I reduce my risk of IR?
A key method of reducing your risk of IR or mitigating against its effects is to reduce your body weight &/or weight carried around your waist is you are identified from the charts above to be of increased risk (based on BMI), or high/very high risk (based on waist measurement).
To decrease body weight &/or waist circumference, diet and lifestyle changes are recommended, which should incorporate the principal nutrition and activity advise in the UK.
|Carbohydrate||Approximately 50% of total dietary energy|
|Free Sugars||No more than 5% of total dietary energy|
|Sugar-sweetened drinks||Consumptions should be minimised|
|Fat||No more than 35% of food energy 4 (33% total dietary energy)|
|of which saturates||No more than 11% of food energy (10% total dietary energy)|
|Salt||No more than 6g for adults|
|Fibre (AOAC)||30g per day for adults|
|Fruits and Vegetables||At least 5 portions of a variety per day|
|Fish||At least 2 portions (2 x 140g) a week, one of which is oily.|
|Red and Processed Meat||For adults with relatively high intakes of red and processed meat (i.e. over 90g/day) to consider reducing their intake to a population average (about 70g/day)|
|Moderate activity||Adults should aim to be active daily. Over a week, activity should add up to at least 150 minutes (2.5 hours) of moderate intensity activity in bouts of 10 minutes or more – one way to approach this is to do 30 minutes on at least 5 days a week.|
|Vigorous activity||Alternatively, comparable benefits can be achieved through 75 minutes of vigorous intensity activity spread across the week or combinations of moderate and vigorous intensity activity.|
|Strengthening||Adults should also undertake physical activity to improve muscle strength on at least two days a week.|
|Sedentary Behaviour||All adults should minimise the amount of time spent being sedentary (sitting) for extended periods.|
Making Diet and Lifestyle Changes
Making change to diet and lifestyle can be difficult, so to give yourself the best chance of success this involves the setting of SMART goals!
Being aware of the process of change helps us to identify where we are and understand that if things do not go as you expected, that this is normal. In fact, these periods provide opportunities to learn from the experience and strengthen how you go about things in the future.
As we have seen there are several things that we can do to improve our nutrition and activity levels to reduce our risk of IR but remember to think ‘SMART’ about it!