How much HbA1c drops with diet and exercise (and how long it takes)

"If you look after yourself, you will improve." Fine. But by how much, and when? Without those two answers it is impossible to know whether you are on track, and impossible to get through the first few months. Let us go to the figures.

First, the calendar

The most important thing you can understand: each thing improves at a different pace. If you expect everything to move at once you will quit in week three thinking it does not work.

How much it drops with exercise, without touching your diet

In people with type 2 diabetes, programmes combining aerobic and resistance exercise lower HbA1c by around 0.5 points on average.

That may sound small. Put it in context: dropping half a point — from 7.5 to 7.0 — is equivalent to lowering your average glucose by about 14 mg/dL sustained around the clock. And you get it with no drugs, while gaining muscle and improving blood pressure, mood and sleep.

What matters most is the dose: in the analysis of studies that figure comes from, more than 150 minutes of exercise a week lowered HbA1c by 0.89 points, against 0.36 with less. Aerobic, strength or both: it all works, and strength also protects your muscle.

How much it drops with weight loss

Here the effect is of a different magnitude, because you are attacking the cause and not just the symptom.

In the DiRECT trial, the proportion of people who reached full remission by weight lost was: 7% with less than 5 kg, 34% between 5 and 10 kg, 57% between 10 and 15 kg, and 86% with 15 kg or more.

And in prediabetes, losing about 7% of body weight together with 150 weekly minutes of activity reduced the appearance of diabetes by 58% over almost three years.

The full picture

Putting the above together, this is what can reasonably be expected from three months of well-executed work:

These are rough ranges from what I see in my practice, not data from a study: every body responds at its own pace.

Two honest warnings about this table. First: these are ranges, not promises — individual response varies and depends on duration and on how much pancreatic reserve you retain. Second, and more important: the higher you start, the easier it is to drop a lot. Going from 9.5 to 8.0 is usually faster than going from 7.0 to 6.5. The last few tenths are the expensive ones.

Why it sometimes does not drop

If you have done things right for three months and the number has not moved, there are explanations worth checking before you blame yourself:

• You repeated the test too early. This is cause number one.
• You lost weight, but muscle too. Without enough protein and resistance work you lose muscle mass, and muscle is your main glucose consumer. You get thinner, but you improve less than you could.
• You sleep badly or live under high stress. Cortisol raises glucose, and no diet compensates for six months of five-hour nights.
• HbA1c is misleading you. Anaemia, iron deficiency or certain haemoglobin variants alter the result. If your meter and your lab report disagree, tell your doctor.
• Your medication changed. Sometimes you improve and a dose is reduced at the same time: the number stays the same, but you really did improve.

How to measure properly

1. Record your starting value and the date.
2. Repeat after three months, no sooner and not much later.
3. Measure your waist too. It often improves before the blood test and keeps your motivation alive.
4. Keep all your test results together. The trend says more than any single value.

To translate your number into average glucose, here is the calculator.