Read: Weight Watchers' tough turnaround

No matter whose numbers you believe, it's clear that most wellness programs have fallen short of projected results.

Not surprisingly, wellness vendors today have largely abandoned ROI in favor of a new sales pitch.

Rather than focus on financial returns, they highlight the related benefits of wellness that go beyond reductions in medical claims—benefits like reduced mortality and greater quality of life, knowledge and social functioning.

The vendors are quick to note that these benefits are hard to measure.

Should we settle for this story of soft benefits when we have reached a point where more than 2 in 3 Americans are overweight and where experts predict that 52 percent of the population will have diabetes or pre-diabetes by 2020?

Maybe, instead of throwing in the towel on measuring results, we should try to find out why wellness programs have fallen short … and we should fix them.

My 25 years as an actuary analyzing the results of workplace benefits programs for some of the nation's largest companies has led me to one irrevocable conclusion: The key to jumpstarting the ROI of wellness programs is to focus on food.

Read: The limits of exercise in losing weight

We hear over and over that the diabetes and obesity epidemics can be blamed on Americans' sedentary lifestyles and poor nutrition.

Of these two factors, poor nutrition has by far the greatest impact on health status. The State of U.S. Health – 1990 to 2010 (as reported in JAMA, Aug. 14, 2013) reports that dietary risks have almost three times the impact on both mortality and disability as low or no physical activity.

Yet most broad-based wellness programs implemented by employers invest disproportionately in fitness, stress reduction, and tobacco cessation relative to improving nutrition.

Why is the most consequential of the four pillars being given short shrift?

Many wellness companies simply haven't developed effective solutions to manage unhealthy eating.

Traditional approaches to improving nutrition haven't worked. Making individuals order special foods, or go on diets or track what they eat is unsustainable.

Telling people to eat more vegetables and fruits and less sugar and fat isn't adequate.

Nor is haranguing them about the link between obesity and chronic disease. As BJ Fogg, Director of the Persuasive Tech Lab at Stanford University, notes, "We shouldn't believe that providing information leads to action—we humans aren't so rational."

To be sustainable and effective, nutrition guidance has to fit our lifestyles, not the other way around.

Diet or no diet, we want to be able to go out to restaurants with our friends and family. We want to eat in company cafeterias with our co-workers. When we're home, we want to be able to choose between cooking for ourselves or ordering out.

And we desperately need a way to counter the billions spent on advertising enticing us to eat fast food and junk food.

There's no question that eating well is complicated.

For the average person, choosing the right balance of fiber, carbs, fats, sugar, vitamins, and sodium is as confusing as playing the stock market.

Not to mention the challenge of counting grams, managing portion size, and trying to understand the seven-syllable ingredients listed on food labels.

If we are to eat better as a nation, we need something easy, something that takes into account the complex social factors that surround our eating decisions.

We need experts doing the hard work behind the scenes—linking to grocery store chains, to tens of thousands of restaurants across the country and to food-service vendors in our company cafeterias—to make sense of the nutritional content of these meals. We need to know what are the healthier choices that surround us, whether we are at home, at work or on the go.

And we need all of this information personalized to match our dietary needs (whether vegetarian, vegan, pescatarian or paleo), our health status (diabetic, hypertensive, etc.) and our allergies.

Fortunately, a handful of companies are beginning to tie all of this information together, marrying the latest in digital technology with evidence-based personalized solutions to point us to healthy choices wherever we choose to go.

In this new world, simple solutions to help us navigate the complex maze of food choices at home and away, and to make eating well simple, are as close-to-hand as our smart phones.

No longer are we required to become experts in order to navigate the nutritional landmines around us.

It won't be long before even our doctors get on board with easier nutrition solutions. Some forward-looking physicians have already started to replace medication prescriptions and the associated myriad of side effects with personalized food prescriptions that we can carry on our phones.

In doing so, they are following in the footsteps of the father of Western medicine, the Greek physician Hippocrates, who advised over 2,000 years ago, "Let food be thy medicine and medicine be thy food."

If we hope to make workplace wellness a lasting success, rather than a flash in the pan, we would be wise to embrace that same advice.