Despite periodic applications of strict eating regimes and moderate exercise, I remain a stone overweight. I suffer from joint and back pain and have had operations on my wrists for carpal tunnel syndrome and on my shoulders for calcium build-up.
I've developed a flaky scalp and eczema in my eye sockets, of all places. Though I gave up smoking years ago - well, almost completely - at Christmas I caught pneumonia, like some Victorian waif.
If anything, the psychological side of getting older is worse than the physical side. Being self-employed, my working week alternates between depressing inactivity and high-stress bursts of writing, often about subjects I initially know little about.
I have to ask strangers personal questions - once, in a packed and disapproving press conference, I asked Angelina Jolie if she had an eating disorder - which I find deeply embarrassing.
Worse, I feel awash in the modern world. What are Snapchat and Spotify and should I be using them? Who is Kendall Jenner and should I care? These anxieties only make me grumpier.
Every weekend, when I should be feeling at my most relaxed and happy, a black cloud of depression descends on me as I contemplate the working week ahead.
Though I have a nice home, am not in debt and have been with my lovely wife, Ann, for 20 happy years, fear of the future crushes me down. I feel a failure.
The fact that there seems to be no remedy for this perfect storm of middle-aged woes only makes me feel worse.
But then I was put in touch with Dr Josh Axe. Despite sounding like a Bond villain ("Do you expect me to get better, Dr Axe?" "No, Mr Curtis, I expect you to die!"), the lantern-jawed American is "a certified doctor of natural medicine, a doctor of chiropractic and a clinical nutritionist with a passion to help people get healthy by using food as medicine", says his website.
He believes, as did the father of medicine, Hippocrates, that many ailments have their root in the gut, and that by treating the gut we can improve not only our physical health, but also our mental state.
To this end, his latest book has the snappy title Eat Dirt: Why Leaky Gut May Be The Root Cause Of Your Health Problems.
The book says our obsession with cleanliness, over-prescription of antimicrobial and antibiotic drugs, and reliance on processed, chemically enhanced food can upset the natural balance in the body between "good" or neutral bacteria and "bad" bacteria. This has resulted in an "epidemic of leaky gut syndrome".
Basically, the wall of the gut becomes weakened and permeable, allowing "toxins, undigested food particles and other invaders' to leak out into the body and bloodstream.
Ewww, gross!
Dr Axe's analysis of the basic effects read like a checklist of my symptoms. He claims he can alleviate them through diet, exercise, supplements and a resistance-building exposure to "healthy" dirt through horseriding, dog-fondling or walking barefoot through grass.
He even claims his programme helped his mother survive a resurgence of breast cancer.
Dr Axe lives in Nashville, Tennessee, with his wife, Dr Chelsea Axe, where they "enjoy making gluten-free pizza on the weekends and paddle boarding in the ocean".
Not only did Dr Axe set up the (slightly sinister sounding) Exodus Health Center in 2008, he advised the U.S. swimming team on nutrition during the 2012 Olympics and is in demand for public appearances.
This means he travels a great deal. So, I can't consult him in person or even via Skype. Instead, he diagnoses me by email.
I send him two sheets of A4 detailing my lifestyle, medical complaints and state of mind. He responds two days later, telling me, unsurprisingly, that he is "confident" I am suffering from leaky gut.
He says this may account for my joint pain, digestive problems, flaky skin and "brain fog" (which I didn't know I had, but which I immediately realise I do).
"I also think your low feelings could be a result of leaky gut," says Dr Axe. "New research on the gut-brain connection suggests there is a direct link between healthy bacteria in the gut and a healthy emotional state."
The programme to alleviate my condition is straightforward, but drastic. First, caffeine and alcohol must be "eliminated immediately". ("If you must drink alcohol, try to limit yourself to one drink per week," he says, which to me sounds like telling someone to only eat one crisp from a party-sized bag of Kettle Chips - impossible.)
High-sugar foods and grains must be eliminated, too, so no bread, rice, cake, biscuits or sweets. Fruit is ok. Phew!
I should eat food rich in B vitamins including "grass-fed beef and green leafy vegetables"; rich in magnesium, such as nuts, avocado and sea vegetables; and rich in omega-3, such as "wild-caught fish".
I should also eat "foods that are easy to digest and healing", including coconut, olives, cruciferous vegetables (broccoli, cabbage, cauliflower, kale), pumpkin seeds, chia seeds and flaxseeds.
Damn! I hate coconut. And pumpkin. Really, who has time for chia seeds? But his book tells me chicken is ok: it contains copious chicken recipes.
I'm glad to see Dr Axe allows pan-frying rather than just steaming or grilling, and is not keen on raw veg, which can be hard for the gut to break down, particularly for those with "inflammatory bowel disease", which I am also convinced I have.
Dr Axe suggests supplements including L-glutamine powder to heal the gut, fish oil to boost adrenal function, selenium, which "relieves oxidative stress", vitamin B12 and ginseng - all are easy to find in Boots or Holland & Barrett.
"Soil-based probiotics that will replenish the good bacteria in the gut" are harder to track down, and expensive. The other things he suggests - ashwagandha, rhodiola, tulsi - draw blank stares.
He doesn't suggest I go horse-riding or buy a dog, which disappoints Ann, who has always wanted a pet.
But he does want me to do high-intensity interval training - short bursts of high-speed exercise followed by short recovery periods - up to four times a week.
He also suggests I "avoid negative environments" and surround myself with "positive people who will be encouraging", which is easier said than done. And he urges me to "take the steps to heal from any past emotional trauma, whether that means seeing a therapist or joining a faith community".
Dr Axe is American, remember.
Blimey! It's a lot to do all at once, so I approach it in steps. On day one, I start taking the supplements and cut out coffee, which is easier than I expected, and go on the diet.
The day before, Ann cooks a vast joint of grass-fed sirloin, so I live off that with vegetables and salad for about three days, with fruit for breakfast and more fruit with yoghurt and honey for a treat. (Woo hoo!)
The rest of the time it's pan-fried organic chicken and line-caught salmon (I confess I resorted to farmed salmon several times), with broccoli, asparagus and spinach. For carbs, there's the occasional sweet potato.
Over the weekend, I reduce my alcohol intake before stopping on Monday (ok, ok - Tuesday).
From Dr Axe's website, which really is impressively comprehensive, I learn that I can adapt my usual forms of exercise, swimming and cycling, into high-intensity workouts, so I do those every weekday.
I can't afford a therapist, but I do go to church on the Sunday, which is not something I normally do.
There, a combination of stressful factors - screaming children, obscure hymns, not knowing when I'm supposed to sit, stand, speak or shut up - seems likely to induce new traumas, rather than heal past ones.
But, you know, overall it worked. After two weeks, I felt calmer, fitter and healthier.
Certainly, I felt more smug. Some, but not all, of my digestive symptoms abated. I lost 1.8 kg. I didn't suffer too badly with cravings for sweet things, and not at all for caffeine, though I did miss bread. I slept better and my "brain fog" cleared.
Most crucially, for the first time in months, possibly years, my second weekend under Dr Axe's regime passed without that black fog of depression gathering around my soul.
(Though, I confess, I did fall off the teetotal wagon at a lunch party on the Saturday.)
Ann reports that I've managed to ratchet my mood at least a couple of notches further up the cheerfulness scale. I haven't assaulted an errant computer printer or muttered "Oh, for God's sake, really?" under my breath on a bus for nine days. I feel more cheerful, even a slightly nicer person.
But oh, the boredom of it. If I had time (and cash - grass-fed beef isn't cheap) to work through all of the recipes in Dr Axe's book, it might be different. But I live a busy life, which dictated that I ate the same basic diet of chicken-or-fish-plus-veg all the time, often having the same thing cold for supper that I'd eaten warm for lunch.
Most boring of all was drinking water almost all the time. And it must be said that taking seven supplements every morning is a real chore.
So, after two weeks, I am modifying Dr Axe's programme - though not axing it completely, so to speak. I fear that constant adherence to it might reactivate the very grumpiness it initially alleviated.
I'll keep to the basic nutritional guidelines, which strike me as sensible, and to the exercise, which made me feel better.
But I may let the odd slice of sourdough slip through. And while I hope to continue to moderate my alcohol intake, I'll probably do something more like the 5:2 diet - five days off, two days on - than Dr Axe's policy of teetotalism.
Maybe make that the 4:3 booze diet. Or the 3:4. Anyway, I hope that my gut will be slightly less leaky, my demeanour slightly less grumpy, than they were before.
But sorry, Dr Axe, tonight I may order a takeaway. And with a big, cheerful smile on my face, I may ask them to deliver it as fast as they can. Chop chop!
Brain fog
Causes: High-sugar diet, overuse of antibiotics
Foods to avoid: Cow's milk, wheat, bananas
Eat more: Immunity-boosting garlic and grapefruit. Substitute smoothies for soups and broths
Anger and frustration
Causes: Excess fatty food, which puts pressure on the liver and gall bladder
Foods to avoid: Fatty foods (even healthy fats), white sugar and carbohydrates. Non-organic dairy products
Eat more: Raw and dark-green leafy vegetables and green fruits
Depression
Causes: Stress causes the release of hormones cortisol and adrenaline, which halt the growth of beneficial gut bacteria
Foods to avoid: Caffeine, alcohol, sugar and grains
Eat more: Purple and dark-blue food such as berries, grapes and purple cabbage
Angst
Causes: Food allergies and intolerances particularly to gluten or dairy products
Foods to avoid: Both of the above
Eat more: Healthy fats, including coconut and olive oil
Highly strung
Causes: Overeating and under-chewing
Foods to avoid: Caffeine, fried or processed food
Eat more: Fruit and vegetables
