Food, activity and diabetes

Food and activity do more for type 2 diabetes than any single tablet, and they are part of the treatment rather than a preliminary to it. In type 1 diabetes they matter differently: not as treatment, but because insulin has to be matched to both.

There is one piece of safety information that older writing on this subject consistently leaves out, and it belongs at the top: for anyone using insulin or sulfonylurea tablets, exercise can cause hypoglycaemia — during it, and for many hours afterwards. That is not a reason to avoid exercise. It is a reason to know about it before starting.

Activity, and the hypo question

Exercise lowers glucose in two ways: muscles take up glucose while working, and the body becomes more sensitive to insulin for a period afterwards. For someone not on glucose-lowering medication, that is simply good. For someone whose insulin dose was calculated for an ordinary day, it is a change that has to be accounted for.

The part that catches people out is the delay. The raised sensitivity persists long after the activity has finished, so a hypo can arrive in the evening after afternoon exercise, or during the night after evening exercise — commonly many hours later, and often while asleep, which is where it is least likely to be noticed. Repeated unnoticed night-time hypos are one of the ways people lose their awareness of hypoglycaemia altogether.

What follows from that, for anyone on insulin or sulfonylureas:

• Check glucose before starting, and again afterwards. A glucose sensor makes this considerably easier and shows the direction of travel, which a single reading cannot.
• Carry fast-acting carbohydrate, and do not set off without it.
• Expect to check more often than usual in the hours following, including before bed after evening activity.
• Adjusting insulin doses or carbohydrate around exercise is a conversation with the diabetes team. The adjustments are specific to the person, the insulin and the activity, and they are not something to work out from an article.

Two situations where exercise is not the right move. If glucose is already low, it needs treating and time to come up before starting. And if glucose is very high with ketones present, exercise can make the situation worse rather than better — that is the territory of the team's sick-day and ketone instructions, covered under living with diabetes.

How much, and what kind

The UK recommendation is the same as for everyone else: around 150 minutes a week of moderate activity — brisk enough to raise the breathing but still allow conversation — or 75 minutes of something more vigorous, plus strengthening activity on two days a week. Breaking up long periods of sitting matters in its own right, separately from the exercise total.

Both halves earn their place here:

• Aerobic activity — walking, cycling, swimming, dancing — improves insulin sensitivity and does the most for cardiovascular risk, which in diabetes is the thing that matters most.
• Strength work builds muscle, and muscle is where a great deal of glucose is taken up and stored. It is routinely treated as optional and should not be.

Walking remains the most accessible starting point, and the 150 minutes does not have to arrive in one piece — short bouts count, and a ten-minute walk after a meal has a measurable effect on the glucose rise from it.

Starting gradually is sensible, mostly because doing too much at once produces the aches that end new routines in the second week. Anyone who has been inactive for a long time, has heart or kidney disease, or has advanced eye changes should ask before taking up anything vigorous: some forms of retinopathy make heavy straining and high-impact activity inadvisable, and that is worth checking rather than discovering.

Feet deserve a mention that general exercise advice does not give them. Where there is any loss of sensation, a blister or rub can go unnoticed and heal badly, so well-fitting shoes and a look at the feet afterwards are part of the routine rather than fussiness.

Food: there is no diabetic diet

This is the single most useful thing to say about it. There is no prescribed list of permitted and forbidden foods, and the special diabetic foods that used to be sold were a bad idea — no benefit, generally expensive, and often containing sugar alcohols with a laxative effect. They are no longer marketed that way, and nothing is lost.

What matters is carbohydrate, because that is what raises glucose: how much of it, what kind, and how it is spread across the day.

In type 1 diabetes, the work is matching insulin to the carbohydrate in a meal — counting it, and learning how different foods behave. That is what structured courses teach, and it is what makes eating normally possible rather than eating restrictively.

In type 2 diabetes, the question is the overall pattern, and UK guidance deliberately does not mandate one diet. Several work: a Mediterranean-style pattern, a lower-carbohydrate approach, straightforward portion control. The evidence favours whichever a person can actually keep to for years, which is a more useful criterion than any ranking of diets.

The things that come up consistently:

• Sugary drinks are the clearest single thing to drop. They deliver a large amount of fast carbohydrate with no fullness attached.
• Fibre — wholegrains, pulses, vegetables, fruit with the skin on — slows the glucose rise and helps with fullness and with cholesterol.
• Fruit is not off the menu. Whole fruit behaves quite differently from fruit juice, and the belief that people with diabetes should avoid fruit is a persistent and unnecessary restriction.
• Lower-carbohydrate eating genuinely suits some people and is now a recognised option rather than a fringe one. One caution: anyone on insulin or sulfonylureas who cuts carbohydrate substantially needs their medication reviewed at the same time, or they will have hypos.
• Alcohol can cause hypoglycaemia several hours later in people on insulin or sulfonylureas, which is poorly known and lands at night. Eating alongside it helps; so does telling whoever is present, because a hypo is easily mistaken for drunkenness.

A referral to a dietitian is one of the things UK diabetes care is supposed to provide, and it is worth asking for rather than assembling a diet from the internet.

Weight

For type 2 diabetes, weight loss has a larger effect than anything else available, and enough of it achieved soon enough after diagnosis puts a meaningful proportion of people into remission — the figures are under living with diabetes.

Three things keep that honest. The amount needed to improve glucose, blood pressure and cholesterol is far smaller than the amount needed for remission, so a modest loss is worth having on its own terms. Supervised programmes work considerably better than resolve. And none of this applies to type 1 diabetes, where weight loss is not a treatment.

One caution, because this is where diabetes advice does harm. Food and weight are under constant measurement in diabetes, and for some people that tips into a disordered relationship with eating — more common in type 1 diabetes than in the general population. Anyone for whom any of this is becoming distressing rather than useful should say so, and diabetes and mental health covers where that goes.

What this is not

Food and activity are powerful in type 2 diabetes and they are not a replacement for medication that has been prescribed. Many people need both from the start, and needing tablets or insulin is not evidence of having failed at the diet. Nothing here is a reason to stop or reduce anything without a conversation first.

See also treating diabetes, and diabetes for the rest of this section.