You may have seen the reports this week that physical exercise is ineffective as a treatment for depression. Well, I don’t agree. John Campbell, Professor of General Practice and Primary Care at Peninsula College of Medicine and Dentistry at Exeter University, described it as a ‘carefully designed research study’. But was it?

Here’s what happened. Researchers from the Peninsula College, together with those from Bristol University, took 361 patients aged 18 to 69 with mild to severe depression, and divided them into two groups. Half were given the ‘usual care’ and half were given ‘usual care’ and, in addition, advised to take exercise. At the end of one year the two groups were assessed. Those assigned to the ‘exercise group’ were slightly less depressed but the difference was not considered large enough to be statistically valid.

So, if you suffer from depression, can you drop the exercise? Well, of course, exercise has other well-known health benefits, so that wouldn’t be a good idea on physical health grounds anyway. But the two big flaws in this study were, firstly, that it relied upon self-reporting of exercise levels and, secondly, that the ‘exercise group’ only did, on average, twice as much exercise as the others (assuming they didn’t exaggerate).

Now, most people don’t take much exercise. So testing the effects of doing twice as much is far from conclusive. Twice nothing is nothing. All that happened was that the ‘exercise group’ met PE trainers three times face to face and had 10 telephone calls. If I’d been running the trial I’d have had regular organised exercise sessions at, maybe, three different levels.

Now, it doesn’t take a lot of exercise to make a difference but it does have to be vigorous. For example, as I reported in my book How To Be Happier just eight minutes of exercise increases noradrenaline (norepinephrine for US readers) up to ten times, while 12 minutes increases endorphins five times, and 30 minutes almost doubles PEA. All these chemicals are mood boosters. But the research that produced these findings was conducted on people exercising vigorously, which is to say, at around 70 per cent of maximum heart rate. At that level you’d still be able to talk but you’d be puffing.

The researchers took the view that it wasn’t realistic to ask depressed people – possibly middle-aged, overweight people who didn’t normally exercise – to, say, get a bicycle and cover 20 miles a day. Fair enough! But that’s not a comment on the efficacy of exercise. All this study has shown is that ambling along behind a dog does little to combat depression. My advice is to ignore the headlines. Keep exercising. The more the better.

Do you say you haven’t got time for exercise? Well, could you manage around 20 minutes a week? If so, you can make a major contribution to your health, fitness and longevity. That’s the conclusion of scientists who have been investigating High Intensity Training (HIT). In fact, HIT goes back to the work of Arthur Jones in the 1970s (and even to the work of the long-ignored Dr Gustav Zander in the late 19^th century) but the latest discoveries set a whole new standard. Provided you’re not in the fifth of the population who are ‘non-responders’ then, according to Jamie Timmons, professor of ageing biology at Birmingham University, you can get by with just three minutes of HIT a week (plus a little gentle exercise to warm up first).

Usually it’s all done on an exercise bike but the principle can be adapted for other activities. The regime is two minutes of gentle exercise to warm up followed by 20 seconds as fast as you can go, followed by another two minutes of gentle exercise and another 20 seconds and finally a third bout. Do that three times a week and that’s it. Four-fifths of people see worthwhile improvements in their insulin sensitivity (reducing the likelihood of diabetes) as well as their aerobic fitness and for the 15 per cent who are ‘super-responders’ the improvements are substantial.

But what interests me especially is the impact on happiness. It’s well established that exercise improves the level of several ‘happy chemicals’ in the blood but, as I reported in my book How To Be Happier, it’s always been thought the exercise needed to be vigorous and fairly prolonged. I’m going to give this new HIT protocol a try and I’ll let you know how I get on.

One of the big stories of the week is that eating red meat shortens life. Researchers led by An Pan at the Harvard School of Public Health studied data on 121,000 doctors and nurses covering a period of up to 22 years. It turns out that a daily serving of red meat increases the risk of dying from cancer by 13 per cent and of dying from heart disease by 19.5 per cent. The critical level seems to be 42 grams of red meat a day – below that you’re okay, the further you are above it the more dangerous it gets. And processed red meat (hamburgers and sausages, for example) turns out to be worse than unprocessed.

If you’d bought my book Help Yourself To Live Longer (Teach Yourself, 2010) you already would have known this. I pointed to studies which suggested that eating meat less than once a week improved life expectancy by three to four years.

Fat has a lot to do with it. So do nitrosamines. But there is another element. Other research suggests that a low protein diet promotes longevity. No one really knows exactly how much protein a human being requires but a widely accepted figure is 0.75g per kg of body weight per day. Meat is obviously high in protein. One good steak provides roughly double that amount. On the other hand, a vegan would struggle to reach it.

So if you want to live longer, become a vegan. There’s more. You’ll no longer be responsible for the suffering and death of farm animals. That should make you feel both relieved and happy.