The Fat Smash Diet

Medically Reviewed by Christine Mikstas, RD, LD on June 13, 2024
4 min read

If you’re ready to “smash” bad eating habits in favor of building good ones, The Fat Smash Diet might be for you.

The name may sound radical, but the plan is based on healthy principles. For instance, you eat a lot of fruits and vegetables.

It's not an overnight fix. Give it 90 days, and you'll change your relationship with food.

The plan comes from Ian K. Smith, MD, who served on President Barack Obama’s Council on Fitness, Sports & Nutrition and is the author of other diet books including Shred and The 4-Day Diet.

This diet has four phases:

  1. Detox: The program starts with a 9-day vegetarian “detox” phase based on meals of mostly produce. Meat, fish, pasta, and alcohol are forbidden.
  2. Foundation: This phase loosens up. You can have meats, fish, and some alcohol and healthy grains and fats. You exercise a bit longer, too.
  3. Construction: You add more variety to the diet to sharpen your focus on portion control.
  4. Temple: You keep adding more foods, and work to get back on track if you had any slip-ups on the plan.

The plan starts out strict, but it becomes pretty easy to follow later on, and it leaves you with good habits that last.

Limitations: You have the most limitations during the diet’s first phase. It only lasts 9 days, but it's a big change from the typical American diet.

Cooking and shopping: You can buy many foods ready-made. But preparing at home is recommended so that you control portion sizes and know exactly what's in it. The book includes easy sample recipes for each phase.

Packaged foods or meals: No.

In-person meetings: No.

Exercise: Exercise is required, and you'll work out longer and harder in each phase. You start with at least 30 minutes of cardio training, and gradually add more time. You start weight training in the last phase of the plan.

Vegetarians and vegans: Yes. You just need alternate proteins to substitute for the meats, eggs, and dairy products.

Gluten-free diet: Gluten isn't the focus of this diet, but if you want to go gluten-free, you can make that work.

Cost: Grocery costs are likely to be similar to what they were before you started the plan.


Does It Work?

There is no research on the success of this specific plan or the long-term results people can expect. The plan includes a very restrictive first phase and semi-restrictive second phase, but overall it is based on healthy eating principles, which make weight loss likely.

Is It Good for Certain Conditions?

Except for the first two phases, the plan is in line with major health organization recommendations for weight loss. It promotes eating a diet low in saturated fat and high in fruits and vegetables, making it a sensible choice for people with high cholesterol, diabetes, high blood pressure, or heart disease.

That being said, you will still need to talk to your doctor for guidance on medication changes and how much exercise is right for you. Changes in diet, exercise, and weight loss affect the amount of diabetes, blood pressure, and other medications you might need.

You also still need to follow the advice of your doctor or nutritionist about how much salt and carbs you should be eating.

The Final Word

The strengths of this diet are its focus on healthy eating and exercise and the fact that it does not exclude food groups.

The diet might work for you if you want lots of direction about what to eat, though it may not provide enough long-term support, because it’s only a 90-day plan.

The cons are that it starts off very restrictive, isn’t very flexible, and doesn't have a plan for weight maintenance.

Beware: Regaining lost weight is common when maintenance -- and the challenges that go along with it -- is not a focal point of a diet.

The plan gradually increases exercise to an hour a day, so if you hate to exercise, or have physical limitations, it may not be for you.

There’s also a fair amount of food preparation involved, so if you prefer dining out or eating convenience foods, you might find this diet tough to follow.

Keep in mind that the health risks associated with "detox diets" are not known. So if you try the diet, be cautious and listen to your doctor and your body.