The coffee diet encourages you to drink at least 3 cups (720 ml) daily while restricting calorie intake. Though it may result in short-term weight loss, it may not be a sustainable diet in the long term.

The coffee diet involves drinking several cups of coffee daily while restricting calorie intake to around 1,500 calories per day.

Some people have reported success in short-term weight loss with the diet. However, it has some significant downsides, and most of its benefits need more research to support them.

The diet may also be too restrictive to be sustainable for many people. It may also be unsafe for some people, particularly those who are pregnant or nursing, teens, and children.

This article reviews the coffee diet, including its potential benefits, downsides, and whether it’s healthy.

The coffee diet was popularized by the book “The Coffee Lover’s Diet” by Dr. Bob Arnot.

In the book, Dr. Arnot claims that drinking coffee several times daily can boost your metabolism, burn more fat, block calorie absorption, and decrease your appetite. He was inspired to write the book after studying the people living on the small Greek island of Ikaria, which has a large population of healthy older adults.

He believes their health and longevity result from their high intake of antioxidant-rich coffee.

Antioxidants help target oxidative stress, a cause of cellular damage, in the body.

How it works

The coffee diet plan involves drinking a minimum of 3 cups (720 ml) of light-roast coffee per day. Light roasts tend to be richer in polyphenol antioxidants than darker roasts.

Dr. Arnot places particular importance on the type of coffee you choose and how it’s brewed. He recommends a lightly roasted, whole-bean coffee that you grind at home and prepare using filtered water. On the diet, you can have as much coffee as you want, caffeinated or decaffeinated, as long as you reach your 3-cup (720-ml) minimum. However, you should avoid using sugar or cream.

He also recommends replacing one meal daily with a homemade, high fiber, green smoothie. Suggested smoothie recipes are featured in the book.

Your other meals and snacks should be low in calories and fat and rich in fiber from whole grains, fruits, and vegetables. The author also encourages readers to avoid highly processed foods, such as frozen meals and refined snack foods, in favor of whole foods.

In the book, Dr. Arnot’s sample meal plans contain about 1,500 calories per day, which is likely much fewer calories than a typical person consumes. Appropriate meals for this diet include tofu and vegetable stir-fry over brown rice, or a grilled chicken salad with a vinaigrette dressing.

Some people have reported weight loss success with this diet, likely due to the calorie restriction involved. In addition, coffee consumption has been linked with weight loss.

Coffee is rich in caffeine and antioxidants called polyphenols, which have several health benefits, including decreased inflammation and free radical damage.

When it comes to supporting weight loss, coffee appears to have three potential benefits: decreasing appetite, reducing fat storage, and increasing metabolism.

May decrease appetite

Dr. Arnot asserts that coffee can suppress your appetite, helping you decrease your daily calorie intake.

Older research from 2017 suggests that this may be true to an extent. Drinking coffee shortly before a meal may decrease the amount you eat at that meal. However, consuming coffee 3 to 4.5 hours before eating appears to have minimal effect on the amount you eat at the next meal, while caffeine intake 30 minutes to 4 hours before a meal did suppress food intake.

A 2018 randomized controlled trial suggests that coffee may have weak, temporary effects on energy intake and isn’t an effective appetite suppressant.

A 2024 randomized controlled trial suggests that drinking caffeinated coffee at breakfast may increase the desire for sweet foods and lead to a higher fructose intake during the rest of the day.

Caffeinated coffee may help decrease calorie intake for some people, but more research is needed before definitive claims can be made.

Reducing fat storage

A 2021 review of earlier research suggests that coffee may help reduce fat stores. This may suppress the accumulation of body fat. However, it does not reduce fat on its own.

The studies reviewed included older test tube and animal studies, as well as research on human participants.

A 2019 review of earlier research in human participants suggests that caffeine, though not necessarily coffee, may support weight, BMI, and body fat reduction.

May increase metabolism

Caffeinated coffee, in particular, may increase the calories and fat you burn, making it easier to lose weight.

A 2024 review of research notes that coffee stimulates metabolism by between 5% and 20% for at least 3 hours. While half of the increase in metabolic rate results from caffeine and derivatives, the other half’s source is still unclear to researchers.

The individual response to the same amount of coffee can vary between individuals, potentially due to:

  • how quickly they clear caffeine from their body
  • genetics
  • age
  • sex
  • body composition

In the same 2019 review of research mentioned earlier that included more than 600 people, researchers found that greater caffeine intake was associated with decreased weight, body mass index (BMI), and fat mass.

However, much of the research on coffee and metabolism was done in the 1980s and ‘90s. More recent research would help strengthen these findings. However, little recent evidence supports some of Dr. Arnot’s stronger claims.

As part of a balanced eating plan, coffee contains beneficial antioxidants and may help you lose weight by suppressing your appetite and increasing your metabolism.

However, the coffee diet has several downsides.

Excessive caffeine

Although decaffeinated coffee is an option on the coffee diet, many people prefer caffeinated coffee. Plus, many of coffee’s metabolic benefits are attributed to caffeine.

Although drinking excessive amounts of caffeinated coffee can be harmful, caffeine intake of up to 400 mg daily, or about 4 cups (960 ml) of coffee, is generally considered safe for healthy adults. However, if you are pregnant or have underlying health conditions, it’s best to talk with a doctor about how much caffeine is safe for you.

However, caffeine intake may result in several side effects, such as:

  • headaches
  • insomnia
  • anxiety
  • muscle twitches
  • increased urination
  • irregular heart rate
  • gastrointestinal irritation
  • restlessness

Caffeine is also a diuretic, meaning it causes you to excrete more fluid through urine. If you drink a lot of coffee, you may need to use the restroom more frequently. You can also lose important electrolytes like potassium with fluid loss.

Losing too much potassium may potentially lead to a condition called hypokalemia, which can affect your muscle control and heart health. However, coffee-induced hypokalemia is rare.

High blood pressure (hypertension)

Caffeine and coffee may potentially increase the risk of hypertension.

One 2021 study in older adults suggests that habitual coffee drinkers had a higher systolic blood pressure than participants who drank coffee occasionally or rarely.

However, a 2023 meta-analysis of observational studies on the relationship between coffee intake and high blood pressure found that coffee drinkers had a 7% lower risk of high blood pressure than those with the lowest intake.

More research is needed to better understand the relationship between coffee and blood pressure.

Weight regain is likely

Diet plans that drastically reduce calorie intake often result in weight regain due to the changes your body undergoes when you restrict calories. The coffee diet recommends 1,500 calories daily, regardless of sex or body size. This may be too restrictive for some people.

Calorie targets for weight loss should be individualized, based on your sex, weight, and activity level.

Your body adapts to the number of calories you habitually consume. Thus, when you decrease your calorie intake significantly, your body adapts by slowing your metabolism, reducing the number of calories you burn.

In addition, hormonal changes that occur during calorie restriction may increase appetite.

Leptin is a hormone that promotes feelings of fullness and signals your brain to stop eating. However, leptin levels in your body may decrease significantly on low calorie diets, potentially leading to greater hunger and food cravings.

It’s difficult to lose weight on diets that require you to significantly reduce your calorie intake, such as the coffee diet. The end result is often weight regain.

Research suggests that sustainable changes to diet that you can maintain over the long term, and physical activity, are more likely to result in weight loss that you can maintain.

Not safe long-term

According to testimonials, people typically follow the coffee diet for two to seven weeks.

It may be unsafe over the long term for several reasons.

Drinking large amounts of caffeinated coffee could lead to excessive caffeine intake, which may cause several side effects, including insomnia and depression.

The coffee diet may also be too low in calories for some people, making it difficult to maintain weight loss over the long term.

No long-term studies have assessed the safety or effectiveness of the coffee diet.

For these reasons, you should not follow the coffee diet long-term.

The coffee diet is not an ideal weight loss plan.

Unlimited coffee consumption may lead to excessive caffeine consumption. Moreover, its calorie restriction may be too extreme for some people, making weight loss more difficult to maintain over the long term.

Successful weight loss diets often involve only a small calorie restriction, which results in slower, more sustainable weight loss and lessens the negative metabolic changes associated with calorie restriction.

Increasing your protein and fiber intake, decreasing the amount of refined sugars you consume, and exercising regularly may help you lose and maintain weight.

For most people, the most successful weight loss diet is one they can stick to.

For safe and healthy weight loss, it’s best to avoid restrictive programs, such as the coffee diet, in favor of more sustainable plans like the Mediterranean diet, the DASH diet, or the MIND diet.

Or you can work with a dietitian to develop an eating plan you can stick to long term. You can find a dietitian in your area by checking out the Academy of Nutrition and Dietetics’ Find a Nutrition Expert tool.

The coffee diet encourages you to drink at least 3 cups (720 ml) of coffee daily while restricting your calorie intake.

Though it may result in short-term weight loss, it’s not easy to follow in the long run. Excessive caffeine intake may lead to weight regain and adverse effects.

You may still enjoy the health benefits of coffee, but stick to the limit of 4 cups (960 ml) per day or less.