Why do people put on differing amounts of weight?

When we eat, our blood sugar level rises - and both the speed at which it peaks, and then how quickly our bodies deal with that and get it back to normal, is very important to our health. Constant high spikes can lead to type 2 diabetes, as well as us laying down more fat and increasing our risk of other diseases.

Foods have, therefore, been traditionally classified by how much of a blood sugar spike they cause - with "high GI" (Glycaemic Index) foods being thought of as bad for us, and "low GI" as good. Every nutritionist would tell you this. But the Israeli research, led by Dr Eran Segal and Dr Eran Elinav, suggests that it is simply not so.

Once I arrived in Tel Aviv, the team not only took all my vital statistics and medical history, but they gave me a little implanted glucose monitor under my skin, which would monitor my blood sugar levels constantly for the next week. The team's nutritional experts had prepared me six days of menus specifically designed to test my body's response to a few standardised meals, mixed in with some of my personal staple foods.

I'm an accident & emergency doctor, which is something that undoubtedly has an effect on my diet. Rushing around on my feet all day with strange working patterns has meant that eating times can be erratic - and unless I have been super-organised, I am at the mercy of the hospital canteen.

I never buy bread - it's an aisle I just don't even go down in the supermarkets and I live in fear of sandwiches - but I see other people living on them.

I do, however, reach for the grapes - I love them. I can eat bunches of them and feel guilt-free doing so. They are my go to "healthy" snack. Another guilt-free grab is sushi - especially after a day's filming. I snatch a box of salmon nigiri and am off. Now, though, had come my chance to find out what each of these foods was really doing to my body.

Other things, such as stress levels, exercise and sleep can all affect our blood glucose responses, so the research team made me log everything I did throughout the day on a little phone app.

Most importantly, though, because their initial data had suggested that different individuals responded differently to foods, I teamed up with another volunteer of the same gender and age - Leila.

For the next week, Leila and I did and ate exactly the same things together - eating in the same restaurants and carefully weighing our food to ensure that it was as identical as possible. Textbooks said that our bodies should respond to them in a similar way. The Israeli researchers suspected that we wouldn't.

/By BBC/