Last Night's Viewing: The Men Who Made Us Thin, BBC2 The Field of Blood, BBC1

In 1943, Louis Dublin, the chief actuary for US insurance giants Metropolitan Life, published a series of charts that changed the world. Dublin used data from four million policyholders to ascertain the optimal weight for long life. Overnight, more than half the population of America was reclassified as overweight. The Men Who Made Us Thin, Jacques Peretti's engaging follow-up to last year's The Man Who Made Us Fat, was full of such stories about the arbitrary nature of weight and the weight-loss industry.

We learnt about a calorie-counting experiment in 1940s Minnesota that led to one participant chopping off his fingers and saw fantastic period footage of Bernice Weston, head of WeightWatchers UK, announcing: "When it comes to eating, fat people are basically very stupid."

We also met Jane Maas, the Peggy Olson of her day, and the woman responsible for pushing diet supplement Metrecal on an unsuspecting America. "It was almost a cocktail party... the first time dieting had been presented as a sexy way of life," she said. "I don't think the advertising industry really created the necessity of being slim, but I think we fanned it." WeightWatchers' former finance director Richard Samber was less repentant, comparing it to a lottery and remarking that the company was successful because "84 per cent of people have to come back and do it again – that's where your business comes from".

Throughout it all, Peretti kept the tone nicely balanced between curiosity and outrage, although it was hard not to feel dispirited as he talked to the diet pushers themselves, including the charming Pierre Dukan and the oleaginous Venice A Fulton, creator of Six Weeks to OMG.

Hard too not to feel that for all the research, the interesting interviews and the clever use of footage there was little new here. As talking head after talking head lined up to claim that since the 1940s research has shown that most dieters end up not simply putting the weight back on but weighing more before, the temptation to yell, "So what's the solution then, people?" grew stronger. It turned out it was eat less, exercise more. It always is. I'm not sure that I needed an hour of television, however well executed, to tell me so.

Still, Peretti's findings might have been of interest to trainee journalist Paddy Meehan, heroine of The Field of Blood, who appears to have ditched the egg-and-grapefruit diet she was living on. Sadly, we are also without Peter Capaldi's tormented Dr Pete, who died at the end of the first season, although David Morrissey continues to delight as conflicted editor Devlin and Katherine Kelly is clearly relishing playing the new editor-in-chief, a Thatcher stand-in with a Northern accent and a wardrobe that's Joan Collins via Buchanan Street.

It's 1984, with the miners' strike in full cry and the newspaper industry on the brink of change. Paddy has earned a promotion to the night shift, aka the dead hour, which means she spends her time travelling round Glasgow with grumpy George desperately searching for the crumbs of a tale. One finally arrives and they almost blow it by taking a bribe to cover up what looks like domestic abuse but turns out to be murder.

While the television version of The Field of Blood lacks the sense of human fraility of the Denise Mina books on which it's based, occasionally seeming clunky in comparison, its great strength lies in the accurate portrayal of a distant, darker time. Paddy, a young working-class Catholic woman, fights disapproval at home and sexism at work. She's a permanent outsider, not male enough for the newsroom but not female enough for her disapproving mother, and Jayd Johnson expertly captures both her vulnerability and the steel at her core.