National Severe Insulin Resistance Service - Carbohydrates

Carbohydrate containing foods affect your blood glucose levels after eating and are therefore an important focus in the diet for people with severe insulin resistance.

Carbohydrates are found in many foods but the main sources are foods such as: potato, bread, rice, pasta, breakfast cereals, crisp-breads, fruit, milk, yoghurt, cakes, biscuits, sweets, chocolate and sugar.

When carbohydrate containing foods are eaten, they are broken down by digestion into glucose molecules (sugar) and absorbed into the blood stream causing blood glucose levels to rise. The hormone insulin normally regulates blood glucose levels within the range 4-8mmol/L. It is released by the pancreas and helps to move glucose (one of the body’s fuels for energy) from the bloodstream into parts of the body where it is either stored or used for energy. Blood glucose is measured in units of milli moles per litre (abbreviated to mmol/L). Usually the body produces just the right amount of insulin to allow the glucose to enter the cells, bringing the glucose levels back into the normal range in the bloods stream.

When you have severe insulin resistance the insulin you produce or inject does not work as effectively at moving the glucose from the bloodstream into the cells resulting in glucose levels remaining too high. This will prevent the glucose that comes from the carbohydrate foods to be taken up by the cells. Because of this insulin resistance a larger dose of insulin is needed to do the same job.

Carbohydrate type:

The more processed the carbohydrate is the faster the rise in blood glucose levels will be after eating and the harder it is to keep glucose levels in the normal range. The rate at which blood glucose rises after eating different carbohydrates is referred to as Glycaemic Index (GI). GI is a way of measuring the effect individual carbohydrate foods has on blood glucose levels. It recognises that not all carbohydrates affect blood glucose in the same way. Foods are given a GI number according to their impact on blood glucose levels. Glucose is used as the standard reference (GI 100) and other foods are measured against this. The lower the GI the slower the absorption. The GI of a food is determined by how quickly it is digested, which is influenced by many things. Processed and cooked foods tend to have a higher GI. Some types of fibre will lower the GI of foods.

• Low GI carbohydrates are digested more slowly so they stay in the system longer causing a slower, steadier rise in blood glucose levels. Including more foods with a low GI in meals can reduce post meal peaks in blood glucose levels and help keep blood glucose more even over the day.
• Low GI foods give a feeling of fullness for longer meaning hunger pangs don’t return so quickly and can help when trying to lose weight.
• Studies show that low GI foods can improve the body’s sensitivity to insulin and can help improve blood fat levels such as “good” cholesterol. Research shows that people who have an overall low GI diet have a lower incidence of heart disease.
• Although many vegetables and some fruits have a small effect on blood glucose levels, the fibre in them will reduce the GI of any foods they are eaten with. Therefore adding vegetables, in particular, to meals will help reduce the GI of meals eaten with.

The table below shows a list of refined carbohydrates (High GI) to avoid and options lower in GI and fat to try instead. Portion sizes are discussed on the following pages.

Carbohydrate portion – How much?

Irrespective of the GI of the food the larger the portion of carbohydrate eaten, the more insulin the body needs to help you absorb it to use as energy. As explained above when you have insulin resistance the body is not able to recognise the large amounts of insulin and so will not be able to effectively absorb even standard portions of carbohydrate foods.

Therefore an important part of the dietary management is to eat smaller amounts of carbohydrate and to spread the carbohydrate out over the day. This involves avoiding ‘doubling up’ on carbohydrate foods in one meal, for example try to avoid having bread and potatoes (e.g. sandwich and chips) or bread and pasta together (spaghetti and garlic bread).

The exact amount of carbohydrate that you will be able to tolerate in one meal will vary person to person. Therefore by completing a food diary along with testing your blood glucose levels we can help you work out the amount your body can tolerate. Please ask to speak to a Dietitian if you have not been given a food diary. If you would find it useful the Dietitian can then give you suggested quantities of carbohydrates to have at meals and snacks. Often people with insulin resistance cannot tolerate more than 50g of carbohydrate (excluding salads and non-root vegetables) at one sitting. Often this would be less at breakfast time as this is when insulin resistance is highest. There is an additional information sheet with meal and snack ideas.

If you would be interested in learning about how to calculate the carbohydrates in foods please ask us for information or a referral

Should I try a carbohydrate free diet?

A lot of people ask about carbohydrate free diets. A carbohydrate free diet requires the majority of the diet to be replaced by sources of fat and protein and minimal fruit and vegetables are allowed. This can be very damaging for people with severe insulin resistance as the fat will be inappropriately stored and can result in worsening metabolic complications. This is why we are encouraging people to instead follow a reduced carbohydrate and low fat diet.

Protein foods

When protein rich foods are digested, the amino acids produced do not rely on insulin for utilisation. Protein is also known to help us feel fuller for longer and can help with a large appetite. Therefore when cutting back on carbohydrate it is beneficial to eat additional lean protein foods.

For example

• Beans and pulses (baked beans, lentils, mixed beans),
• Chicken without skin, lean pork and beef,
• Vegetable proteins such as Quorn or Tofu,
• Low fat diary such as yoghurts and cottage cheese for example.

For all foods, labels should be checked that they have less than three grams of fat per 100grams of the food.

Vegetables

Vegetables are high in fibre and low in both fat and carbohydrate. Exceptions to these, which should be eaten in moderation are avocados, potatoes and parsnips.

Contacts/Further information

Dietitians Catherine Flanagan and Lisa Gaff: 01223 216655

Diabetes specialist nurse in SIR: 01223 348790 and 01223 768625