TV can be a grumpy old beggar at times. There you are, made it through Christmas and the regulation ten tons of Quality Street, and there’s an extra inch or three on the old waist to prove it. So what? It will come in handy for January. If it is good enough for bears to pile on the fat for winter ...

No, no, no, says television, wagging its bony finger in your face. It’s a new year, a new start, and 2019 must see a new, improved you, so spit spot and let’s be having you watching programmes that show how to go about it. Sigh.

First up was Tom Kerridge’s Fresh Start (BBC2, Wednesday 8pm). Having lost 12 stones in the past five years, the Michelin-starred chef has both talked the talk and walked the walk on diets. He made a winning impression last year with his Lose Weight for Good series, and now he’s back, and going back to basics, showing families how to ditch convenience food and cook from scratch.

The eight families chosen, “my gang” as he called them, were clearly in need of a hand. One lot had carrots in the fridge, but those were strictly for the guinea pigs. Kerridge took things slowly, starting the beginners off with bangers and mash and pasta with sauce, although blow torching peppers for the latter seemed a tad advanced for newbies. If you were that raw at cooking, would you have a blow torch in the kitchen?

Kerridge is a naturally matey sort, so well suited to this type of programme. His enthusiasm is infectious, and he passes on his vast knowledge of food in an easy-osey way, as if he is just some bloke who has learned to throw a few things together. One would call him the new Jamie Oliver if the old one wasn’t still very much around; but you have competition, Jamie lad.

As does every popular science presenter from Chris and Xand van Tulleken. The greedy pair have not just one selling point but two: they are identical twins, and doctors to boot, making them the ideal presenters for The Twinstitute (BBC2, Wednesday, 8.30pm).

Using themselves, and 30 other pairs of identical twins as subjects, the two set out to test competing theories, including what would shift weight faster, diet or exercise, and was meditation a better way to cope with pain than swearing?

The duo tested the latter personally and my goodness they earned every penny of their presenting fees. It turned out that meditation was more effective than cussing (tell them that on the maternity ward boys, I dare you) and a low calorie diet narrowly beat exercise.

The experiments were not entirely practical, with the exercisers having to put in two hours a day in the gym, for example, but the programme got its points across in an engaging way. Next week: power napping v banking sleep. Set your alarm for that one.

Those naughty boys behind The Windsors, writers Bert Tyler-Moore and George Jeffrie, were back with a sitcom pilot, Island of Dreams (BBC2, Thursday, 10pm). A riff on the Love/Celebrity island format, it had Richard Branson (played by Harry Enfield) playing host to a collection of famous folk ably impersonated by Morgana Robinson, Samantha Spiro and others. I particularly liked Spiro’s fake JK Rowling, complete with, bizarrely, a West Country accent.

Island of Dreams just about worked as a half hour show, but without a lot more gags it would struggle as a series. There were some choice pops, though, especially at Branson and his trains, and oh to have been a fly on the wall at the pre-broadcast meeting with the lawyers when a particular JK Rowling/Daniel Radcliffe scene was discussed.

Jeremy Wade’s Mighty Rivers (STV, Friday, 8pm) was given a prime slot between episodes of Coronation Street, rare for a wildlife programme but deserved. Wade described himself as a biologist and “extreme angler”, which meant he went after big fish rather than your regular kind. The survival of large fish is a canary in the coalmine test of a river’s wellbeing. This week, Wade was on the Danube, which flows through ten countries and is on the endangered list of rivers, even with stringent EU regulations meant to protect it.

His first task was to find out how the Beluga sturgeon were faring. With their eggs selling for £3000 a pound, the Beluga had been hunted almost to extinction. It is now illegal to catch them, but that does not stop poachers trying. One discarded net was packed with dead creatures, much to Wade’s distress, but a single Beluga was just about still alive. After cutting it free and administering some quick TLC, it was set free to swim again, ending what had been a rotten old day for Wade on a high. The extreme smile on his face said it all.