How quickly should I lose how much weight?

Hi @Davido Jones, welcome to the forum.
I was in a similar situation five and half years ago, albeit only about 10 kg overweight.
At that time, I was convinced that persistent weight loss is almost never achievable and all diets will fail, i.e. weight loss regimes are not sustainable. If you simply reduce calorie intake you start to lose weight, but you will always feel hungry. Even worse, after some time your base metabolic rate, BMR, will reduce and you will need fewer calories. At this point you stop losing or even start gaining weight again. You will feel hungry and miserable all the time and at some point give up and gain the weight again. There are too many people who then start again this cycle of yoyo dieting.
What convinced me to try weight loss were the books of Michael Mosley on the 5+2 diet. His method involves changing your diet and eating only 600 calories on 2 days a week. To achieve this you will not eat potatoes, pasta, rice, bread on fast days, and mainly eat vegetables, soup, an egg, or a bit of fish and chicken. However it worked, despite having a gruelling travel schedule at the time, I started losing weight and lost 10 kg in about 6 months. Intermittent fasting (IF) does not lower your BMR and has worked for many of us, i.e. we eat normally on other days, and don't feel hungry. I also started exercising and biking, which helped getting me into shape.

I have learned a lot more about nutrition since then. A major point is that carbohydrates are quick fix food. When eating chips, ice-cream or a milkshake you will feel hungry again after 2 hours. Fatty foods, like cheese, full fat yoghurt, eggs, meats on the other hand are more satiating.
Others on this forum decided to reduce carbs intake to low or very low (~20g/day) levels, compensating this with increase of fat and protein. Many reported a reduction of weight without trying.
With such a change of diet a weight loss can be sustained by many here on the forum.

So it appears to me that you are a bit ahead of yourself, but to answer your question directly, losing weight at a rate of 0.5kg up to a maximum of 1 kg a week is possible. Anything above I would consider unhealthy, effectively starving yourself continuously.

How high was your HbA1c and what medication have you been given? if you are on metformin only dieting is fine, but if you are on gluclose lowering drugs, e.g. gliclazide, you need to talk to your GP about how your diet plans will affect your medication.

Davido Jones said:

Hi guys, I was diagnosed today and have been advised to lose weight. I am 1.82 meters tall and weigh 101.5 KG. My doctor wants me to lose 20 KG. What is the advisable loss of weight per week in order to avoid compliactions with the weight loss? Many thanks!

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As you can't just dial up a rate to lose weight I'd say forget it, just control your blood glucose levels and reduce it gently down to normal with the foods you are eating.
I never found it easy to lose weight, it was almost impossible on a high carb low fat diet sheet, but by bringing my blood glucose and HbA1c levels down to normal over a few months I believe I changed my metabolism. Suddenly my clothes were falling off - luckily in private. I thought the elastic must have failed but I had actually lost a lot of weight without even trying.

Davido Jones said:

Hi guys, I was diagnosed today and have been advised to lose weight. I am 1.82 meters tall and weigh 101.5 KG. My doctor wants me to lose 20 KG. What is the advisable loss of weight per week in order to avoid compliactions with the weight loss? Many thanks!

Click to expand...

When my dad was diagnosed in back in the 60s in his early 50s, when diet and exercise were the only treatments for T2D, he was 1.82m tall and weighed 97.5 kg. His goal weight was 77 kg. I don't know high his initial blood sugars were (I was just a kid), but they were high enough to panic my mother who was an RN and our family doc. He was actually hospitalized and put on an 800 calorie/day diet (when I asked what he got to eat he said black coffee, water and beef bouillon) and told to walk. So he spent 8 hours/day walking up and down the hospital corridor. He lost 13.6 kg in 3 weeks and then was discharged and transitioned to a 1500 cal/day diet to lose the rest which he did. He lived to be be almost 80 and besides a life long hatred of beef bouillon, he had no other effects. So it is possible to lose weight quickly and keep it off and not do your body any harm. But you should ask either your doctor or a registered dietician.

I'm another whose weight loss is erratic, but although it goes in fits, starts and plateaux, it does go. Now within 3lb of (self-set) target, I can lose a pound, gain a pound day by day over weeks and then I lose some small amount of weight and it stays off.

For me, I never even expected weight loss to be a part of going low carb/keto. I did that to regulate my blood glucose, and initially when I had plenty of weight to lose, the weight loss was an unexpected bonus. Then I "met" these wise folks here and learned a lot. So the takeaway (!) from that is: we are all different, and our own bodies govern our changes. But if we give them help and time - it happens. Believe me, it happens!

Some need medicine as well as lifestyle changes in order to regulate their blood glucose, and that's fine, but it will impact upon weight loss. The most important matter is the blood glucose control; let the weight follow its own route.

Start putting money by for new clothes......