Zuma is undisputed winner in London's Japanese restaurant stakes

I have not been a good Weight Watcher this year. Stress, travel, eating away from home a lot ... all are enemies of the low fat, portion-controlled diet and regular exercise required for good health. This kind of balance is far easier to strike if you don't go out much. But let's face it, that's not me. (And it were, this would be a mighty boring blog.)

In fact, going out is on the rise now that Piers works up in London and, on days when we're both in town, staying up for dinner seems so much more logical than joining the commuting throng and rolling through the front door starving with a meal still to cook at 8pm. How to dine out a lot and stay Weight Watchers friendly? My latest attempt has been to refine my restaurant choices to Japanese. Low on saturated fats, heavy on fish, great on portion control; it's hard to do an unhealthy binge at a Japanese restaurant. (Although, as you will read below, it turns out it is possible.) Thus over the past three weeks I've been to Shogun, Itsu, Hiroba and Zuma. The last stood out as the finest restaurant of the four, but all had their own advantages.

Shogun has the best atmosphere of the four, especially if you're looking for someplace quiet and intimate. It's in an arched stone basement just off Grosvenor Square, and has fewer than 20 tables in the long, cozy space. There's a small sushi bar with five or six seats at it. A full suit of Japanese armor stands at the end of the room, and areas of the restaurant are divided off by screens of arrows; both a nod to the restaurant's martial name. About half the diners were Japanese, and the staff entirely so. Always a good sign. Sushi, sashimi and tempura were all delicious, though the menu was limited and resolutely traditional. I was disappointed in the lack of combination menus, as we were out for a splurge to celebrate new jobs and would happily have gone for some sort of chef's tasting menu. Though there are a few combos, they're pretty basic and not along gourmet lines, leaving us with a la carte choices.

Splurge we did, though not intentionally. Shogun was the most expensive of everything reviewed here, and it certainly didn't provide better value than anything else. We may try it again, however, as Piers swears that bagging one of the few seats at the sushi bar transforms the experience. (This was one of his regular haunts in the late '80s.) For value for money, however, I have to direct you to Hiroba.

This is, admittedly, one of my regular haunts, located as it is directly across the street from my PR agency and on the flight path between London office and Waterloo station. I go so often that it's long lost any sense of being special, which is why poor Hiroba has never made the blog before. I apologise. I should have mentioned it. Because it's a brilliant option in this part of town and the winner in the value for money stakes in the higher end sushi market.

Like Shogun, Hiroba is staffed and frequented by citizens of the Orient. But there's a less traditional slant here. There are two other Hirobas ... one in LA, and another in Seoul ... and I suspect that explains the profusion of more exotic, multiple-ingredient rolls you'll find on the conveyor belt. That belt snakes through the place and at least half the seats are at it, with three tables right next to it and about 10 tables along the walls. Unless you know exactly what you want, avoid the tables and go for the bar, where a profusion of choices will tempt you to build up a little mountain of plates. Though mostly sushi and sashimi, there are some main course options (mostly tempura and crispy beef) which waiters will heat up for you. The average plate is £3.50, which means you can have a very reasonable light dinner and even if you eat yourself silly you're probably not over the £50 mark (excluding alcohol). The only danger here, of course, is that I always enter intending to do the light, inexpensive dinner and walk out having consumed a feast.

It was the chain Yo! Sushi that introduced the conveyor belt concept to London and it dominates this style of Japanese, with Hiroba being a pleasant exception. Another is Itsu on Draycott Avenue in Chelsea. Yes, Itsu is a chain like Yo! and these days you can't swing a tuna in The City without hitting one. They're know for their quick, pre-packaged, high quality sushi boxes, and the St. Paul's branch provides my lunch most days I work from town. I love the place, but was rather surprised when friends suggested it for dinner. Turns out the branch in Chelsea, like its sister in Notting Hill, is a proper restaurant rather than a fast food place. Like Hiroba, the belt snakes through the restaurant, but here it's been cleverly designed so that it flows by far more tables for four. And thus Itsu Chelsea gets my nod for best sushi place to meet up with friends. It's a festive atmosphere, the sushi's good and the staff is quick to both to bring anything ordered off the menu, and to top up your drinks. A bit more expensive than Hiroba to pay for that Chelsea rent, but generally in the same ball park.

If I'm going to splurge, however, the chef's menu at Zuma is the clear winner. I loved this place when I went almost three years ago (see 26.9.08) but hadn't been back since, mostly because it's over by Harrods and I'm not actually in that part of town too often. After my second outing it's worth reminding myself that this is worth a special trip.

The tasting menu is £60 ... about what we spent at Shogun and a bit more than the other two ... for a five course extravaganza that balances exquisite flavors with beautiful presentation and a few show stopping dishes. You start with a nicely-balanced tuna tartare served in shot glasses on a mound of ice, decorated with fans of fried lotus root that provide a crisp accompaniment to the soft fish. Beside that is a plate of wafer thin sea bass sashimi, kicked up a notch with the addition of truffle oil. Taste buds suitably amused, out comes the "proper" sushi course, with three different plates showing off the skill of the guys behind the bar. Course three brings the cooked seafood, with some of the most succulent black cod I've ever tasted glistening under a sweet and sour marinade. That's served with langoustine tempura, a dish that makes the usual prawn version pale in comparison. The main courses climax with wagyu beef and miso soup. The beef is just one perfectly cooked thin steak, marinated, sliced thin and served on a hoba leaf (a type of magnolia, used to wrap steamed foods in Japan) for two people to split. As with the rest of the procession of food, there's enough here to be generous, but not so much to stuff you.

And then comes dessert. Generally not something associated with Japanese restaurants, but here Zuma breaks the mould. Out comes an impressive platter with three kinds of ice cream, two traditional cakes and a pile of exotic fruit. One of the cakes is a chocolate fondant and, much to my surprise, it was absolutely the best one I've ever had. I've tried fondants on their French home turf, and in many a top European establishment, but it's in this trendy Japanese place that I found the perfect balance of cakey outside, gooey interior and dark chocolate bite. This, of course, entirely defeated the Weight Watchers objective of eating at a Japanese restaurant, but locked my determination to get back to Zuma again soon. Not only is in the best Japanese I've had in London, but my second visit has firmly placed it in my top five restaurants across all cuisines in the capital.