Prediabetes: what to eat and what to avoid, without impossible diets

Being told you have prediabetes is frightening. And yet it is probably the best news you could get among the bad ones: it means you are still in time. This can be turned around, and there is very solid data showing it.

What prediabetes actually is

It is a situation where your glucose is above normal but not yet at the diabetes threshold. Your body is already struggling to handle sugar, but it is still compensating.

These are the values that define it:

These are the American Diabetes Association criteria. In Spain many doctors use the WHO and Spanish Diabetes Society criteria, which are stricter about what counts as prediabetes: fasting glucose of 110 to 125 mg/dL and HbA1c of 6.0 to 6.4%. If your report uses different ones, your doctor's criteria are the ones that count.

One of them falling in the middle band is enough. And they do not all have to agree: it is very common to have perfect fasting glucose and an HbA1c of 5.9, because they measure different things.

The good news, with numbers

The Diabetes Prevention Program is one of the most important studies done on this. It followed thousands of people with prediabetes and compared changing habits with not doing so.

The result: the lifestyle intervention reduced the appearance of type 2 diabetes by 58% over almost three years. In people over 60, the reduction was 71%. And over fifteen years of follow-up, incidence was still 27% lower.

What exactly did they do? Two things, and neither is heroic:

• Lose about 7% of body weight. For someone weighing 90 kg that is just over 6 kg.
• Do 150 minutes a week of activity at an intensity similar to brisk walking. Half an hour, five days.

Six kilos and half an hour a day cut the risk by more than half. That is the real scale of what is being asked of you.

What to eat

I am not going to give you a list of banned foods, because lists of prohibitions have an expiry date. Here are the principles everything else rests on.

Protein at every meal

Egg, fish, meat, pulses, dairy. Protein satisfies, protects your muscle mass while you lose weight — exactly what you want to keep — and cushions the glucose rise of whatever you eat with it.

Vegetables as the base, not the garnish

Fibre slows glucose absorption. Until now vegetables decorated the edge of your plate; from today they are half of it.

Carbohydrates, yes — but whole

The difference between an apple and apple juice is not the calories: it is that in the juice you have broken the fibre and the glucose arrives all at once. Same with a whole potato versus mash, or real wholemeal bread versus white. Whole, not blended. Genuinely wholemeal, not "with added bran".

Good fat, without fear

Extra virgin olive oil, nuts, avocado, oily fish. Fat does not raise glucose and helps the meal satisfy.

Pulses, two or three times a week

Probably the food with the best ratio between what it gives you and what it costs you in glucose. And it is cheap.

What to genuinely avoid

If I could only ask you for three things, these would be the three:

1. Sugary drinks. Soft drinks, juices — including "natural" ones — sweetened coffee drinks. It is glucose with no fibre, no protein and nothing to slow it down. And it does not satisfy: you save nothing on the next meal.
2. Ultra-processed snacks. Pastries, biscuits, crisps. They are designed so you cannot stop, and that is their function, not a failing of yours.
3. Daily alcohol. Empty calories, worse fatty liver — which is at the centre of all this — and ruined sleep.

Three practical changes almost nobody tells you

1. The order of the meal

Eating vegetables and protein first and leaving the carbohydrate for last reduces the subsequent glucose peak compared with eating exactly the same food in the opposite order. It is the cheapest change there is: same plate, same money, same time. You only change the order of your fork.

2. The ten minutes afterwards

A short walk after eating takes advantage of muscle being able to take up glucose exactly when there is most of it circulating. It does not have to be forty minutes: ten after your main meal already counts.

3. Do not eat carbohydrate alone at breakfast

Coffee with biscuits, or toast with jam, is a glucose spike first thing and hunger by eleven. Swap some of the bread or cereal for protein — egg, fresh cheese, plain yoghurt, tuna: glucose usually rises less after breakfast and you stay full for longer.

What you do NOT have to do

No 800-calorie diets on your own. No cutting out entire food groups. No weighing every gram. No "glucose support" supplements bought online.

They all share the same flaw: they do not last. And in prediabetes the only thing that matters is what you can sustain for years, because the risk lasts years too.

When to repeat the test

If you have started changing things, give it three months before repeating HbA1c — that is how long the marker takes to reflect your new situation. I explain it in what HbA1c is.

And if you have already tried and not managed it, it is not a matter of willpower. Almost always it is that nobody gave you a plan that fitted your real life.