Mackie’s celebrity clientele has included: Broadway actress Jennifer Holiday, along with actors Wendell Pierce and John Goodman - transforming 63-year old Terminator 1&2 star Linda Hamilton’s body and performance to a level not seen before in Hollywood for her role of Sarah Connor in the 2019 Terminator Dark Fate movie, at the request of Hollywood creator, producer, and director James Cameron.
Since 2018, Mackie has volunteered his time and resources in support of members of the U.S. Army Special Operations Command – Delta Force – helping these Operators to achieve optimum performance.

He’s previously assisted Special (SEAL) Boat Team 22 during Operation Iraqi Freedom, U.S. Army Ranger Team 5336 during Operation Inherent Resolve, and members of the 159th Fighter Wing.  In 2019, Mackie teamed with a U.S. Army Ranger Medal of Honor recipient to prepare the two oldest Rangers to ever compete in and achieve a top 5 finish in the Best Ranger competition at Fort Benning, Georgia – considered the toughest special forces competition in the world.

In 1998, Mackie’s volunteer work was recognized by the New Orleans Police Department for establishing health and fitness programs for the department. His volunteer efforts continue today with the presentation of the Mackie Shilstone Peak Performance Award - presented to a cadet, who rises above expectations, during the police officer academy training.

While countless professionals – athletes, actors, law enforcement, and special forces and operators - have received career-extending help from the health and fitness guru, Mackie has also transformed the lives of hundreds of non-athletes struggling with health and weight problems, poor nutrition, and a lack of motivation in his hospital-affiliated wellness programs.

Over 43 years, Mackie designed and directed Fitness, Nutrition, Wellness, and Sports Performance programs at such medical facilities as the John Ochsner Heart and Vascular Institute, Ochsner Health Systems, East Jefferson General Hospitals’ Mackie Shilstone Fitness Principle, and Wellness programs at St. Charles Parish Hospital.

With a Master of Arts and Master of Business Administration degrees, Mackie has served as a Clinical Instructor of Public Health and Preventative Medicine at Louisiana State Health Sciences Center, Adjunct Instructor in the School of Allied Health at Nicholls State University, and Adjunct Professor at the A. B. Freeman School of Business at Tulane University.

Mackie has also served as a special advisor to the United States Olympic Committee on Sports Nutrition, and on the Louisiana Governor’s Council on Physical Fitness and Sports.

Mackie has previously served on the Board of Directors of the National Mental Health Association in Washington, DC.

For the last 27 years, Mackie has been the Nutrition and Fitness Expert for CBS affiliate WWL TV Morning News Show – along with his monthly TV segment - Wellness Wednesday. Mackie’s podcast – Maximum Wellness – is available on Apple, Itunes, Spotify, and Android sites.

His seventh book, Stop Renting Your Health—Own It: A Three Step Approach, was published in January 2012, and outlines the same unique, science-based approach Mackie uses with celebrities and sports professionals to improve health, performance and image.

Mackie’s previous book, Body Plan for Kids, is a comprehensive guide for parents to gain control of their child’s weight. It is the first book of its kind to offer specific strategies for eating healthy, getting fit and increasing self-esteem targeted at 8-12-year-olds.

His other books include Lean & Hard: The Body You’ve Always Wanted in Just 24 Workouts, the ultimate strength-building workout for a powerful muscular physique; The Fat Burning Bible, 28 days of foods, supplements, and workouts that help you lose weight, (January 2005); Lose Your Love Handles: A 3-Step Program to Streamline Your Waist in Only 30 Days (Perigee 2001); Maximum Energy for Life (John Wiley 2003), and Feelin’ Good About Fitness (Pelican Publishing, 1986).

Mackie has written articles for health and fitness publications including “Muscle and Body” Magazine, the American Medical Athletic Association Quarterly, The Physiologist, Nola.com, and the Washington Post’s Fantasy League website – The League.

In January 2020, Mackie was appointed to the Advisory Board, Tulane University School of Professional Development, Department of Kinesiology. In October of 2022, Mackie was the keynote presenter at the United States Tennis Association’s annual conference – with the demonstration of how he increased World Champion Serena Williams’ first serve in excess of 125mph.

In 2024, Mackie was featured with episodes in the second season of the Emmy Award winning ESPN+ TV show - In the Arena – the Serena Williams Story.