As Henry Dimbleby and Doctor Chris van Tulleken highlighted in Thursday’s evidence session at the House of Lords Food, Diet and Obesity Committee, ultra-processed and junk food dominate our diets.

There are many reasons for this, but the latest report from Bite Back shows the biggest one. Thanks to their research, we now know that 7 out of 10 of the biggest food companies in the UK are selling mostly unhealthy foods. This represents a huge swathe of the brands all of us see on the shelves every day.

Of course, this is shocking. But it is also a very important reminder of where power sits in the food system – and the economic motives of the largest food companies. Looking at something through the lens of power focuses on the interactions and relationship between political activity and different players in the economy such as big food companies – or in policy-wonk language, the political economy.

So, what is the political economy of junk food? First and foremost, these companies exist to make a profit for their shareholders and investors. It is their "fiduciary duty". And it is incredibly difficult to make big profits from plain fruit, vegetables, pulses and other healthy foods – just ask the fruit and veg growers currently struggling in the UK.

But what if you heavily process those foods into weird and wonderful products with tempting, highly palatable flavours and exactly the right mix of fat, sugar and salt? Well, now you've created something that can sit on the shelf for a long time, be marketed heavily and ultimately is very convenient – not to mention irresistible.

Junk foods are a great way to make money, and hence the junk food cycle we find ourselves in. And in our current political systems, money and size also equate to power to (among other things) influence policy – and to dampen down regulations which might limit a company's ability to sell junk food.

On darker days, I wonder how we will get out of this junk food cycle. But even everyday people know the answer, as we're hearing in The Food Conversation. The government can set limits in the best interest of its public. And people have the appetite for this.

It’s incredibly encouraging that the new House of Lords committee on Food, Diet and Obesity is digging into this important topic. And even more so that Bite Back and its amazing youth advocates are shining a light on the political economy of food.