If you’re struggling to lose weight, you may need to switch gears.
A Korean doctor has devised a four-week metabolic reset program that’s gone viral based on claims it causes rapid weight loss. The Switch-On Diet focuses on intermittent fasting, protein-heavy meals and gut optimization to promote fat burning while preserving muscle mass.
“By the end of Week 1, I noticed less bloating and better digestion,” a gut health blogger recently shared. “By Week 4, I was down [4.5 pounds] of body fat, felt more energized and experienced surprising mental clarity.”
How the diet works
The Switch-On Diet is the brainchild of Dr. Park Yong-Woo. The obesity researcher wrote a book about it over seven years ago.
Each of the four weeks represents a different phase of the program.
Protein is emphasized throughout because it’s essential for muscle growth and repair. Caffeine, alcohol, processed foods and sugar should be avoided, while carbs are OK in moderation.
Restricting carbs allows the body to enter a state of ketosis, potentially reducing gut inflammation.
Fiber in the veggies adds bulk to stool, making it easier to go No. 2, while some research suggests intermittent fasting may boost energy levels.
Week 1
This week’s goal, divided into two parts, is to detox and reset the gut.
Participants should drink protein shakes four times daily for the first three days, take probiotics first thing in the morning on an empty stomach and walk at least an hour a day.
Plain, unsweetened yogurt, tofu and veggies such as cabbage, cucumbers and broccoli are allowed if hunger persists.
This plan continues for the subsequent four days — except a low-carb, high-protein lunch featuring fish, chicken, tofu, boiled pork, low-fat beef or eggs is added to the routine. Flour, dairy and coffee aren’t permitted.
Week 2
Intermittent fasting, which involves limiting eating to a certain time window, begins this week.
Fast for one 24-hour period, preferably from early dinner to the next day’s afternoon snack, so the fast can be broken with a high-protein dinner.
The daily lineup is two protein shakes, a low-carb lunch like rice, vegetables and a protein and a no-carb dinner like vegetables and a protein.
A handful of nuts, white rice, legumes and one morning cup of black coffee get the thumbs up.
Muscle recovery is the aim — avoid high-intensity exercise on fast days.
Weeks 3 and 4
The last two weeks are about enhancing fat burning by extending fasting periods and adding flexibility to the low-carb meals.
Week 3 calls for two non-consecutive 24-hour fasting periods, while Week 4 requires three.
Continue consuming two shakes a day and two low-carb meals. Pumpkins, cherry tomatoes, chestnuts and berries can be eaten — save sweet potatoes and bananas for post-exercise.
After finishing the program, maintain the results with a 24-hour fast and a 14-hour fast once a week.
Before starting the Switch-On Diet
A doctor should be consulted before beginning any diet plan.
Because the Switch-On Diet limits caffeine intake, participants may notice withdrawal symptoms such as headaches, fatigue and irritability.
Eating the same foods can also get repetitive. A TikTok user said last month that she quit the program after five days because while she shed pounds, she got sick of the protein shakes.
And the pros and cons of intermittent fasting are still being ironed out. For example, a 2024 study found that restricting eating to less than eight hours a day increases the odds of death from cardiovascular disease compared to eating in a 12- to 16-hour window.
