Chicago-based Dr. Ian Smith has become well-known for authoring his bestselling “Shred” diet books, offering expert medical and diet advice on national talk shows and working on the “Celebrity Fit Club” TV series. Now Smith says he has opened an exciting new chapter in his career of helping people improve their personal lifestyle — thanks to a chance encounter that has truly changed the lives of many Chicago Police officers.

One Sunday, Smith met Detective Socrates Mabry at his church. The police officer approached the doctor and asked if he would be interested in helping a number of fellow officers attempt to lose weight.

“Are you kidding me?” said Smith, expressing his enthusiasm for Mabry’s request. “That was something that had literally been on my bucket list for some time.

“I would see police officers around town. I know how tough their jobs are, but I would say to myself, ‘I wonder if anyone trains these guys physically, because I know, for many of them, they are so sedentary for so much of the day.'”

That initial chat led Smith to connect with the deputy chief of police, Keith Calloway, who runs Chicago’s police academy. “Over a month and a half we came up with a pilot program,” he said. “It was a six-week program, because that was based on what I had laid out in my ‘Shred’ book, which is a six-week diet program.”

Initially, 150 officers were signed up for what came to be known as the “CPD Shred Challenge.”

Smith said he was delighted by the results of that first wave of officers joining in. “The results of the pilot were so amazing. I was blown away!” That led the department to open Smith’s program to the entire force of Chicago police officers.

That process continues today, with Smith frequently repeating what he started earlier this year.

“Generally, I run two workouts a week at the police academy and then give a lecture on a particular health and diet-related topic. For example, one might be on vitamins and minerals. Another could be about high blood pressure or diabetes,” said Smith, explaining those talks are moved around from one police district to another to make it easier for “officers to have the maximum opportunity to attend.”

Over the years, Smith has changed his opinion about the pros and cons of rapid weight loss.

“I used to concur with what was then the prevailing opinion of experts in our industry, that rapid weight loss was not a good thing, just on the face of it.

“But I have come to realize that it’s not the rapid weight loss per se that’s the problem — it’s the means of how you undertake that rapid weight loss. It’s the process that’s important,” said Smith.

“For example, if you lose the weight by severely restricting your calories and are undernourished, that’s dangerous. But if you get the proper calories and vitamins and minerals in your body and still rapidly lose weight with exercise as a key component, that’s fine.”

Yet, in the final analysis, Smith stressed something he repeatedly has focused on in all of his diet books, including “Shred: The Revolutionary Diet,” ” The Shred Diet Cookbook” “Super Shred: The Big Results Diet” and now “The Shred Power Cleanse,” being published Dec. 29.

“It’s great to lose 30 pounds, or whatever,” said Smith. “But you have to adopt lifestyle choices and changes in how you live. That’s the only way you will continue to keep your weight in balance and live a healthier life.

“I’m always happy to tell someone, ‘I’m happy you lost the 30 pounds, but I’ll be happier if you also say to me, “I don’t skip breakfast in the morning. I’m now staying away from processed foods. I now will eat more vegetables.”

“Those are the changes that have to last forever, if you want to keep the weight off and simply have the chance to live a longer, healthier life.”

Among the celebrities Smith has worked with, he points to two who have adopted his philosophy of sensible diet and exercise choices.

“First of all there’s Maureen McCormick [of ‘The Brady Bunch’ fame] who was a thrill to work with. She worked so hard and was so dedicated to getting herself fit and in shape. … Another is Steve Harvey. As people likely know from watching him on TV, Steve is such a dedicated guy. Once he’s set his mind to do it, he is all in on whatever it is. That certainly was true of him and our ‘Shred’ program.”

Smith is focused on continuing to bring his “Shred” concept of diet and exercise to far more than just famous celebrities.

“Just like we had the diet and exercise challenge with the Chicago Police, we’re next kicking off a big cleanse challenge with the officers, beginning Jan. 1,” based on his new book.

Beyond his books and TV and radio appearances, Smith loves how social media have broadened his horizons — as they have for millions.

“It’s obviously pretty simple. It’s now so much easier to reach my audience. Before [social media existed], I had to ask permission to go on a platform to deliver a message, whether it was on a radio or TV show or in a newspaper article.

“Now people can find me online without the middle guy and that’s providing such great, easy access to the message I’m trying to put out there.”