Before taking up her current role as senior performance nutritionist at sportscotland institute for sport, Riach worked at Celtic. That was in the mid-nineties and it would be an understatement to say initially she faced an enormous job. It was an era when some of the food scoffed by players would make Usain Bolt's infamous meal of chicken nuggets at the 2008 Beijing Olympics seem like haute cuisine.
"A key area of weakness was definitely post-match recovery at away games," recalls Riach. "It was fine at home, because we could feed them at the stadium, but at an away game, yes, people did want to stop to get chips. So we fitted out a kitchen on the team bus, put a chef on board and fed them on the way home. It sounds remarkably simple and straightforward, but proved very effective."
She did not stop there. "When I first started, the players had boiled chicken and baked beans for their traditional pre-match meal - and didn't use sports drinks," she says. "I introduced foods with good-quality carbohydrates and protein which were also low in fat. Things have come a long way since then, partly due to a change of culture in the management but also because of the influx of foreign players who had a much better relationship with food."
Riach worked under managers Dr Jozef Venglos, John Barnes and Martin O'Neill before moving to Newcastle United when Glenn Roeder was in charge. She then did a stint at Aston Villa when O'Neill was manager there.
Six years ago she decided on a change of direction, joining sportscotland, based in Stirling. Heading a full-time team of four, her role involves overseeing the painstaking planning of the dietary needs of more than 200 Scottish elite athletes across all 17 sports at the 2014 Commonwealth Games.
Be it cyclists, swimmers, triathletes, weightlifters or lawn bowlers, Riach knows every morsel being put into their mouths - right down to the tiniest microgramme. "We look at meal patterns, timings, quantity and quality - it's not just about eating lots of bananas as people tend to think when it comes to sports nutrition," she says. "It's about making sure the diet is of the best possible quality and not only meets all the nutritional requirements for performance but, if you are working with younger athletes, growth too."
Another key part of her role involves determining how to best utilise an athlete's genetic body composition. For this, she employs the study of human measurements - called anthropometry - involving high-tech scans and devices such as callipers.
"Anthropometry is used to analyse mass, height, muscle circumferences, skin-fold thickness, bone lengths, breadths and depths," she says. "With any kind of endurance sports or those with a weight category, if you have any excess - be that fat or muscle - it can hinder performance."
But this is far from a one-size-fits-all process. "Swimming, for example, always used to be about trying to make athletes leaner, but we now know that if you make swimmers too lean, they sit lower in the water which can actually make them slower because they have more drag."
Among the most challenging sports, says Riach, is the triathlon, comprising swimming, cycling and running. "There's a fine balance between having enough power in the swim and on the bike, but not too much muscle bulk so that it slows you down when you are running," she says. "Alongside anthropometry we look at an athlete's maximum oxygen capacity and their running economy, then tailor that to the individual."
Then there are sports such as weightlifting, wrestling and judo which have specific weight categories. "You can make your weight category and still be of relatively high body fat," she says. "We want athletes to be the leanest and most powerful they possibly can."
To that end Riach and her team are working closely with Sunday Herald Six To Watch weightlifter Georgi Black. The Kilmarnock-based athlete previously tipped the scales at 75kg (11st 11lb) but is hoping to reach 63kg (9st 13lb) for the 2014 Commonwealth Games. It is a strategic move which, if the 23-year-old continues to maintain her lifting power as her weight drops, should help move her into the medal zone next summer.
"We have developed a real-time dietary-analysis package," says Riach. "When an athlete fills in their electronic food diary, a dietician is sent an email to say that Georgi, for example, has just entered her breakfast.
"We know what her calorie budget is, how many grammes of fat or protein and all the micro nutrients she's eaten, then can monitor that meal by meal. If she gets to lunchtime and has eaten three quarters of her calories for the day, we can work out how to meet her nutrient requirements for the remainder of the day without going over her allowance.
"It's up to our team to ensure we are trimming that right down to the grammes and microgrammes so she has enough to train and compete - but at a level that will continue to eat away at any excess body fat and gradually bring it down.
"Monitoring all of that we have collected some nice anthropometric data so that, hopefully, when she wins her medal, we will be able say: 'Here's how we did it.'"