How much of losing weight is about what you eat and how much of it is about exercise?

80% diet.  Weight loss requires a daily calorie deficit.  It is far easier to decrease your calorie intake than it is to burn the same amount of calories via exercise.  You also have to accept that if you want to loose weight and keep it off, you will need to permanently change what and how much you eat.

Weight Watchers, which strives for real-world healthy eating and activity levels, instructs that for most of its members, it's about 85% how much and what you eat, and about 15% activity.

While someone who is extremely active (professional athletes, people whose jobs are eight hours of activity) may find that isn't true for them, it is for most adults.

Of course exercise has many health benefits, even if it isn't the secret to weight loss. It uses up calories, which helps with weight loss, and it builds muscle mass, which helps with weight maintenance after loss.

Losing weight is about the combination of both eating less and exercising more. The idea is to find the balance. Why don't you give a try to one of fitness apps, say, MyFitnessPal or Eat This Much. You can read the details here https://agilie.com/en/blog/how-to-create-a-diet-an...

Those services can help you find the best approach that works for your body. I hope, it'll help you.

Like has been said already, eat LESS and move MORE.

It's free to do and you don't need to give someone money to patronise you for it.

Why people can't understand that is a mystery.

Portion control. I got unwell in 2015 and lost 2 stone within about 2 months. Still I was able to eat chocolate and doritos everyday cos Id have about 50g of both along with one meal

You can lose weight with diet alone but exercise gets you more fit physically. On the other hand, even if you exercise the whole day, if your diet is off, you won't lose weight.

Most all of it is about eating fewer calories.  Exercise is good for you, but very few people find it causes them to lose more than a few ounces without calorie restrictions.

It depends how much you eat, and how much you exercise. It's not rocket science. Eating adds calories, exercising subtracts calories. If you add more than you subtract, you gain weight. If you subtract more than you add, you lose weight. 

NO. The balance is about how much in ingest vs how much you burn.

What you eat determines how healthy you are either way.