Do Detox Diets Work? By Natalie Digate Muth, MD

Do Detox Diets Work? By Natalie Digate Muth, MD

If your holiday diet consisted of eating too many heavily processed and artificial foods, you may be thinking about adopting a “detox” this new year.

With an ultimate goal of purging the body of harmful 21st century toxins — food additives, pesticides, pollutants, and other synthetic compounds — and with glowing promises of increased energy, clearer skin, headache relief, decreased bloating, and perhaps even weight loss, detoxing sounds like an ideal solution.

But does it really work?

Do these regimens safely help the body rid toxins better than the normal metabolic processes of the liver, kidney, skin, lymph nodes, and other bodily systems?

The Basic Ingredients of a Detox Diet

All detox diets are some combination of fasting, food restriction and supplementation.

They typically begin with a “cleansing phase,” which is typically two or three days of only liquids. Brown rice, fruit, and steamed vegetables are added until about a week later when other foods — except red meat, wheat, sugar, eggs, and prepackaged foods — may be reintroduced. This final phase is expected to be followed indefinitely for maintenance.

Of course, with no standard definition of a “detox diet,” programs vary considerably.

Most include elimination of caffeine, nicotine and alcohol, and many restrict meat and solid foods altogether. The diets also tend to involve consumption of large amounts of liquid, fiber, and raw vegetables — ingredients that are thought to purge the gastrointestinal system of accumulated harmful substances.

A variety of “cleansing boosters” may be incorporated — herbal laxatives, “colonics” (aka enema, a flushing out of the rectum and colon with water), probiotics to repopulate the natural intestinal flora, and antioxidants.

Some programs even include relaxation therapy, such as massage, sauna, aromatherapy baths, deep-breathing exercises, and walking.

The (Lack of) Science Behind Detox Diets

No evidence supports that harmful chemicals accumulate in the body (in fact, the liver and kidneys are pretty good at getting rid of bodily toxins). And even if toxins did accumulate in the body, there’s no reason to believe that these detox diets would get rid of them.

Toxicologists A. Jay Gandolfi, an associate dean for research in the college of pharmacy at the University of Arizona, and Linda Birnbaum, director of the experimental toxicology division of the Environmental Protection Agency made the following points in a LA Times article:

  1. high volumes of liquid consumption could theoretically help remove water-soluble chemicals like arsenic, but not fat-soluble chemicals (which make up most pollutants)
  2. fiber consumption may help eliminate toxic chemicals that accumulate in the liver, but not chemicals that are located in other parts of the gastrointestinal system
  3. raw vegetables have no special detoxifying properties other than that their high fiber content can further help bulk up stools
  4. most chemicals of concern are fat-soluble and so are stored in fat. The best way to get rid of these potential toxins is not through a detox diet, but through weight loss. Slender people get rid of toxins more quickly than overweight and obese individuals.

Possible Dangers

While consuming a lot of fiber and staying hydrated are healthy when done in moderation, using colonics and laxatives that are intended to “purify” the digestive tract are dangerous.

Their use can lead to metabolic disturbances, fainting episodes, dehydration, and muscle cramps, among other complications. The more extreme programs also leave individuals protein- and nutrient-depleted. Among other consequences, this can lead to decreased lean muscle mass and slowed metabolism.

But What About the Great Benefits Countless Detox Followers Pronounce? 

Benefits may exist, but they likely are not due to detoxification.

The decreased bloating is likely from eating less food; the clearer skin from increased hydration; and the decreased headaches exercise and relaxation components of the program, and psychological factors.

That’s not to say all forms of detox diets should be strictly avoided. In fact, there may be some benefit in a short-term (1-3 days) laxative-free “detox” program, but not for its purification.

As a health-promoting practice, committing to a detox regimen helps people stop and consider the healthy and unhealthy components of their lifestyles, and make changes — eating less, examining health habits, and getting rid of the junk like processed foods, nicotine, caffeine, and alcohol.

Some dietitians even recommend a “gentle cleanse” to clients. That is, a healthy dietconsisting of primarily fruits, vegetables, non-meat proteins, and lots of water while excluding substances such as nicotine, caffeine, and alcohol.

In the end, a short and moderate “detox” regimen (free of additional supplements, laxatives, and colonics) may serve as an incentive to improve a chronically unhealthy lifestyle, though remember, it does not purify or cleanse the body of toxins.

Recommendations if You’re Starting a Detox Diet

  • Define what a detox diet means to you. Is it a commitment to eat more healthfully, minimizing exposure to processed foods and chemicals? Or, something more extreme, which might include severe deprivation or laxative and colonic use? If it’s the former, by all means continue to consume a diet rich in fruits, vegetables, whole grains and water; and low in or free of alcohol, caffeine, and nicotine. If it’s the latter, consult both a physician and dietitian to minimize potential harm, and get more information on how to try a detox diet without significant risk to your health.
  • Make sure you understand the benefits and risks of detox regimens, and explore possible alternative methods that might help improve your health and purify (such as an overall healthy diet that is not nutritionally deficient and regular physical activity).
  • Recognize that children and adolescents; pregnant and breastfeeding women; older adults with impaired kidney or liver function; individuals with chronic illness such as diabetes, cancer, heart disease, or gastrointestinal disease; individuals with eating disorders such as anorexia or bulimia; those with irritable bowel syndrome; and individuals on blood thinning medication are at high-risk for negative health outcomes from following a detox diet.


  1. Clemens R and Pressman P.  Detox diets provide empty promises.  Food Technology. 2005; 59(5): 18.
  2. MacGregor HE.  “Purification, or just a purge?; liquid fasts, colonics, pills, vegetables. Detox regimens that promise to remove harmful chemicals are wildly popular- but the science behind them is scant.”  LA Times. 23 October 2006, Health, Features Desk, Part F: Pg. 1
  3. Dixon B.  “Detox”, a mass delusion. The Lancet Infectious Diseases. 2005; 5: 261.
CrossFit: New Research Puts Popular Workout to the Test By The American Council on Exercise

CrossFit: New Research Puts Popular Workout to the Test By The American Council on Exercise

Newly released ACE-sponsored research gauges the calorie burn and intensity of two popular CrossFitTM workouts.

“It can kill you…I’ve always been completely honest about that,” said Greg Glassman in a now somewhat infamous New York Times interview about CrossFit, the high-intensity workout program he founded in 2000.

A former gymnast and gymnastics coach, Glassman designed the no-nonsense and notoriously tough workout regimen by combining functional strength training with gymnastics, circuit training and endurance exercise. It started with a single gym in Santa Cruz, Calif., and grew slowly from there in a cult-like manner, mostly the territory of underground fitness types and hardcore military guys. But it has since blossomed into a full-fledged global workout craze, attracting everyone from soccer moms and college coeds to middle-aged executives and cubicle dwellers.

Today, CrossFit boasts more than 7,000 CrossFit gyms (except they call them “boxes”) worldwide, more than 35,000 accredited trainers, more than 10 million Crossfitters (nearly 60 percent of whom are women) and even recently inked a 10-year multi-million dollar deal with Reebok to sponsor the annual CrossFit Games, which crowns the man and woman deemed the “Fittest on Earth.”

While all of this newfound popularity certainly lessens some of CrossFit’s original underground fitness street cred, it does not diminish the strenuousness of the workouts themselves. Anecdotally, the body sculpting and endurance/strength-building success stories of CrossFit are many. But surprisingly, very little real scientific research has been conducted on CrossFit.

Spurred on by CrossFit’s immense popularity, the American Council on Exercise enlisted researchers from the University of Wisconsin, LaCrosse, to gauge the energy expenditure and relative exercise intensity of a pair of CrossFit workouts.


Led by John Porcari, Ph.D., head of the University’s Clinical Exercise Physiology program, and Paige Babiash, M.S., the research team first recruited 16 healthy, moderately to very fit female and male volunteers between the ages of 20 and 47. Next, to establish a quantifiable baseline of fitness, each subject completed a maximal exercise test on a treadmill while researchers gathered data including heart rate (HR), VO2max and ratings of perceived exertion (RPE). This data also enabled the research team to create a regression equation for each subject to predict their individual VO2max based on HR data. This is key because it would be impossible for the subjects to complete the CrossFit workouts while wearing the bulky VO2max metabolic testing gear.

For this study, researchers selected two separate CrossFit workouts—each of which has been used as an official CrossFit Workout of the Day (WOD). For each WOD the goal is to complete all of the prescribed repetitions in the shortest amount of time possible. The first WOD used in the testing, named Donkey Kong, incorporated burpees, kettlebell swings and box jumps. Each exercise was performed three times, with the number of repetitions decreasing each time. During the first round, each exercise was performed 21 times, the second round 15 times and the final round nine times. Between each exercise, subjects climbed a flight of stairs.

The second WOD selected is one of the most popular WODs within the CrossFit community. It’s called Fran and consists of just two exercises: thrusters (a front squat into a push press with a barbell) and assisted pull-ups. This WOD was performed in the same sequence as the first. Each workout included a five-minute warm-up, a skill phase, a WOD and a five-minute cool-down phase. Prior to completing each of the CrossFit workouts, each subject was required to practice the selected exercises and then demonstrate to researchers that they were proficient at each one.

During actual testing, researchers recorded HR for each subject every minute throughout the entire workout and RPE was assessed after each round. Additionally, an overall RPE was taken at the end of the workout session, while blood lactate concentration was tested at the beginning and upon completion of each CrossFit WOD.

Anecdotally, researchers noted that the workouts seemed very difficult for most of the subjects. “It didn’t matter their skill or fitness level, and it didn’t matter how long it took them to complete the workouts,” says Paige Babiash, M.S., “Each person was extremely exhausted at the end.”


Immediately following both testing sessions, the researchers crunched the data and plugged each subject’s HR results into his or her individual regression equations to predict VO2max for each WOD session (Table 1).

Table 1. Average Exercise Responses to Two CrossFit Workouts

Crossfit Workout 1
Mean ± SD

Crossfit Workout 2
Mean ± SD
Heart Rate (bpm)

167 ± 7.56
162 ± 12.5

158 ± 13.9
160 ± 7.33

% HRmax
91 ± 5.4
91 ± 3.7
86 ± 7.4
90 ± 5.5
VO2 (mL/kg/min)
36.6 ± 9.14
44.8 ± 7.75*
32.4 ± 5.31
44.2 ± 8.85*
% VO2max
86 ± 6.0
83 ± 4.7
78 ± 13.9
81 ± 10.2
12.9 ± 2.74
20.6 ± 2.80*
11.6 ± 2.22
20.4 ± 3.69*
Session RPE (6–20)
16.9 ± 0.99
16.1 ± 1.54*
15.3 ± 1.17#
14.3 ± 1.25#*
Change in Lactate (mmol/L)
10.2 ± 3.20
11.6 ± 2.96
8.46 ± 1.88#
11.0 ± 4.41#

* Significantly different than females (p<.05).

# Significantly different than workout 1 (p<.05).

Values represent Mean ± SD.

On average, this study found that caloric expenditure averaged 20.5 kcal/minute for the male subjects and 12.3 kcal/minute for females.That said, the amount of time it took each participant to complete the WODs varied greatly (some did it in less than 5 minutes, while others took as long as 20 minutes), a discrepancy that definitely affected the averages for total number of calories expended during each workout. Still, researchers found that males burned an average of 169.6 calories for Workout 1 (completing the workout in an average time of 8 minutes, 23 seconds) and 112.5 calories for Workout 2 (average time: 5:52). Meanwhile females averaged 117.2 calories for Workout 1 (average time: 9:08) and 63.9 calories for Workout 2 (average time: 5:52).

As for heart-rate responses, during the first round of both CrossFit workouts HRs were elevated to an average of 90 percent of maximum heart rate (HRmax), which was maintained throughout the remainder of the workout (Figure 1). Given that fitness industry guidelines suggest maintaining a training range of 64 percent to 94 percent of HRmax to improve cardio endurance, these CrossFit workouts both met the mark.

Similar to the HR responses, VO2 increased immediately during the first round of both workouts and increased slightly with subsequent rounds (Figure 2). Researchers found that VO2 averaged 80 percent of VO2max during both CrossFit workouts, indicating that the subjects were exercising well above their anaerobic thresholds. This is at the higher end of industry recommendations of maintaining 40 percent to 85 percent of VO2max to improve cardio endurance.

The vigorous intensity of a CrossFit workout was further illustrated by participants’ blood lactate values, which averaged 15.9 mmol/L for men and 12.4 mmol/L for women, both of which are well above the normal lactate threshold of 4 mmol/L. Across the board, subjects’ RPE values for both workouts were rated as “hard” (Figure 3) and the RPEs during Donkey Kong (Workout 1) were markedly higher than those for Fran (Workout 2). 


CrossFit works. For those who already do CrossFit regularly, this is surely no news flash. Based on the high intensity of the workouts tested, researchers conclude that CrossFit does a really good job of helping exercisers improve their aerobic fitness, while burning a fair number of calories in the process. And, like other high-intensity interval-training (HIIT) workouts, one can expect greater increases in aerobic capacity than what is seen with traditional aerobic training, which is typically performed well below an individual’s anaerobic threshold.

Working out more intensely for shorter periods means that exercisers can likely get good results with CrossFit while spending less time exercising, says Babiash. “The two workouts were completed in fewer than 12 minutes, not including the warm-up and cool-down. Yet, despite this short duration, subjects still burned an average of 115.8 calories,” she says. “Seeing the benefits in such a short amount of time is encouraging, especially if you have a busy lifestyle.”

Porcari agrees, but also notes that a pretty big asterisk should accompany all of his team’s findings. “You look at the intensity of CrossFit and it’s off the charts,” he says. “This is not the workout for a 45-year-old person with multiple cardiovascular risk factors. People absolutely need to be properly screened before beginning CrossFit.”

Beyond being potentially risky for many would-be exercisers, Porcari warns that the competitive nature and emphasis on completing CrossFit exercises as quickly as possible may well be a recipe for injury for some exercisers.

“The thing we’ve seen with a lot of these workouts is you go flat-out as fast as you can, but then your form falls apart. You really need to be technically correct with a lot of these exercises or else you’re going to get hurt,” says Porcari. “And it’s nice to be competitive with other CrossFitters, but at what point are you pushing yourself outside the realm of safety?”

Naturally, ACE recognizes that any exercise is better than none and that if CrossFit gets people up and working out regularly, then that’s success. That said, would-be CrossFitters and those who train them should pay close attention to the potential pitfalls outlined by Porcari to ensure that this current fitness craze doesn’t create more injured bodies than fit ones.

A Walk A Day By The American Council on Exercise

A Walk A Day By The American Council on Exercise

The popularity of walking as a fitness activity is growing by leaps and bounds. Low risk and easy to start, walking has proved its health benefits in numerous studies. A classic eight-year study of 13,000 people conducted at the Institute for Aerobics Research under the direction of Dr. Steven Blair found that those who walked the equivalent of 30 minutes a day had a significantly lower risk of premature death than those who rarely exercised.

A regular walking program can help:

  • Reduce blood cholesterol
  • Lower blood pressure
  • Increase cardiovascular endurance
  • Boost bone strength
  • Burn calories and keep weight down

Get Ready

A walking program is simple to start. All you need are comfortable clothes and shoes. It is a good idea to layer loose clothing, keeping in mind that exercise elevates the body’s temperature. Shoes specifically designed for walking are your best option.

Every workout should begin with a brief warm-up and a few simple stretches. Walk around the house or in place for a few minutes to get the blood flowing to the muscles before you attempt to stretch them. Although walking primarily works the major muscles of the legs, don’t forget to stretch your back, shoulders and arms. This will help to loosen up any tension you may be carrying and make your walk more enjoyable, as well as more effective.

Get Moving

Beginning walkers can make their workouts less strenuous by limiting how fast and far they walk. Keep the following in mind:

  • Walk short distances—Begin with a five-minute stroll and gradually increase your distance.
  • Forget about speed—Walk at a comfortable pace. Focus on good posture, keeping your head lifted and shoulders relaxed.
  • Swing your arms naturally—Breathe deeply. If you can’t catch your breath, slow down or avoid hills.
  • Be sure that you can talk while walking—If you can’t converse, you are walking too fast.

Get Fit!

Walking is one fitness activity that allows you numerous options. Once you have reached a point where you can walk a few miles with relative ease, you can start to vary the intensity.

Walking hills, in addition to increasing your cardiovascular endurance, is a great way to tone the legs. Concentrate on lengthening your stride or increasing your speed. And don’t forget to reward yourself after each workout with a few minutes of relaxing stretches to help prevent sore muscles.

Listening to lively music while you walk is also a great way to energize your workout. But if you wear headphones, keep the volume down and watch out for traffic that you may not hear.

Keep track of your progress. Many experts recommend that you walk a minimum of 30 minutes a day, but there are no hard and fast rules. Fit walking into your schedule whenever you can. That may mean three 10-minute walks each day, or even hour-long walks two to three times a week. The best schedule is one that keeps you walking and keeps you fit!

Are Activity Trackers Accurate? by The American Council on Exercise

Are Activity Trackers Accurate? by The American Council on Exercise


By Caitlin M. Stackpool, M.S., John P. Porcari, Ph.D., Richard Mikat, Ph.D., Cordial Gillette, Ph.D., and Carl Foster, Ph.D.

Activity trackers are everywhere these days, but when it comes to tracking steps and calories, are they really accurate? A new ACE-sponsored research study examined five popular activity trackers to determine whether or not they are worth your time or your money.

It’s that time of year, when everyone recommits to a more healthy lifestyle. Increasingly, people are turning to activity trackers—electronic devices that track everything from caloric expenditure to quality of sleep—to help them stay on course and meet their health and fitness goals.

An estimated 19 million devices were in use in 2014, and that number is expected to grow exponentially over the next few years. In fact, a recent report by Juniper Research predicts that the use of activity trackers—also called fitness wearables—will triple by 2018.

While all this new technology is really cool and some of it is really fun to use, very little published research exists demonstrating the accuracy or validity of these devices. How closely do they predict caloric expenditure or track the number of steps taken? Given the increasing prevalence of these devices, the American Council on Exercise enlisted a team of researchers from the Clinical Exercise Physiology program at the University of Wisconsin—La Crosse to examine five popular activity trackers to determine whether or not they are worth your time or your money.

The Study

For this study, five popular activity trackers were chosen: Nike+ Fuelband ($99-$149), Fitbit Ultra ($99), Jawbone UP ($99), BodyMedia FitCore ($99) and the Adidas MiCoach ($199). [Note: Since this study was completed, BodyMedia was purchased by Jawbone.]

Researchers recruited 10 healthy men and 10 healthy women, ages 18 to 44, to participate in the study, which was divided into two parts: one to measure energy expenditure and the other to measure the number of steps taken. The protocol was the same for both studies and they were conducted concurrently.

Along with wearing the activity trackers, subjects wore a portable metabolic analyzer and the NL-2000i pedometer, which has proven reliability, to make an accurate determination of calories burned and steps taken. Each subject performed a series of different exercises wearing all of these devices at the same time; the testing was conducted in two separate 50-minute sessions.

The first session included walking and running on a level treadmill. Each subject walked at a self-selected speed for 20 minutes and then rested for 10 minutes before running for 20 minutes at a self-selected pace.

The second session was completed on an elliptical crosstrainer that worked both the arms and legs; participants completed 20 minutes of exercise at a self-selected intensity. After a break, subjects performed sports-related exercises, including ladder drills, basketball free throws, T-drills and half-court lay-up drills.

After completing both sessions, the values were recorded from each device and compared to the portable metabolic analyzer energy expenditure values and the number of steps taken.

The Results

When it comes to tracking steps, the activity trackers were pretty reliable, says lead researcher Caitlin Stackpool, M.S., with the accuracy depending on the type of exercise being done. All five devices predicted within 10 percent accuracy the number of steps taken during treadmill walking and running, as well as during elliptical exercise (Tables 1 and 2).

Table 1. Comparison of steps taken measured using hand counting compared to steps taken from the activity devices. 
Devices  Treadmill Walking Treadmill Running Elliptical Agility
Actual 2425±177.9 3182±173.9 2631±371.5 805±51.9
Jawbone UP 2403±176.6 3186±171.5 2627±359.0 783±110.1
Nike Fuelband 2273±154.8* 3169±171.2 2580±458.7 533±70.4*
Fitbit Ultra 2425±177.2 2990±313.0* 2630±370.6 645±+90.0*
NL-2000i 2425±178.0 2869±247.1* 2477±471.1* 671±106.9*
Values represent means ± standard deviation.

*Significantly different than actual steps (p<.05).

Table 2. Correlation of steps taken between actual steps and steps recorded from activity devices. 
Devices  Treadmill Walking Treadmill Running Elliptical Agility
Jawbone UP 0.98 0.99 0.99 0.34
Nike Fuelband 0.55 0.98 0.97 0.17
Fitbit Ultra 0.99 0.44 0.99 0.49
NL-2000i 0.99 -0.19 0.70 0.44

During agility drills, however, there was a larger underestimation, but Stackpool explains that this is likely due to the variety of more complex movements.Smaller or quicker steps taken may not always register on the activity trackers, and also appeared to lead to less arm movement, which would then affect the accuracy of the activity trackers that were worn on the arms or wrists (the Fitbit is the only device in this study that is not worn on the wrist).

The devices were a little less accurate when estimating energy expenditure (Tables 3 and 4). Recording energy expenditure is a more complex process, explains John P. Porcari, Ph.D., head of the University’s Clinical Exercise Physiology Department. It also involves incorporating data measured by the device into a regression equation within the devices’ software. This is likely why there was more variation in the recordings.

Table 3. Comparison of caloric expenditure measured using the portable metabolic gas analyzer compared to kcal values obtained from the activity devices. 
Devices  Treadmill Walking  (n=19)

Treadmill Running


Elliptical (n=20)



Actual 109±19.6 240±47.3 161±25.6 90±20.7
Jawbone UP 123±25.2  288±63.6* 161±74.1 63±23.5*
Nike Fuelband 107±24.2 275±56.4* 118±38.0* 77±18.0*
Fitbit Ultra 111±22.8 230±50.5 154±34.1 75±19.2*
Adidas MiCoach 146±18.2* 261±52.4 36±6.8*
BodyMedia FIT Core 112±16.2 210±37.2 129±19.5* 74±19.2*
Values represent means ± standard deviation.

*Significantly different than portable metabolic gas analyzer kcal (p<.05).

Table 4. Correlation of kcals between the portable metabolic gas analyzer and the kcal recorded by the activity devices. 
Devices  Treadmill Walking (n=19)

Treadmill Running






Jawbone UP 0.87 0.69 0.40 0.57
Nike Fuelband 0.49 0.72 0.08 0.47
Fitbit Ultra 0.24 0.63 0.41 0.67
Adidas MiCoach 0.55 0.81 0.65
BodyMedia FIT Core 0.68 0.73 0.47 0.56

The difference between measured and predicted kcals ranged from 13 to 60 percent, with some devices overpredicting and some devices underpredicting. None of the devices were accurate across all the activities for recording calories burned, so picking an activity device to record caloric expenditure may not be the best option.

The Bottom Line

When choosing a device, researchers advise consumers to think about the information they want to track. If looking at steps taken, the Jawbone UP appears to be the best activity device to choose. If an individual is more concerned about calories, there was a wide variety of results, depending on what type of activity was being performed.

“Most devices are pretty good for measuring steps taken during traditional activities,” says Porcari. “Once you start getting outside of that—like elliptical or sports-related movements—it becomes harder to detect actual steps taken.”

“These activity trackers work best for lower-intensity activities such as walking,” adds Stackpool, who thinks these devices are especially beneficial to new exercisers. “It gives them a way to assess where they are, set goals and see improvements.”

And what about caloric expenditure?

“Predicting calorie burn is a complicated thing,” explains Porcari. “People vary how they move their arms, for example. Some are more efficient and some are more variable. Most devices probably won’t get within 10 to 15 percent accuracy because there is simply too much biological variability.”

But that doesn’t mean there still isn’t a benefit to using an activity tracker, says Stackpool. “Activity trackers show people how active they are throughout the day. Being sedentary 90 percent of the time and performing 30 minutes of exercise does not necessarily make a person ‘active.’”

By wearing the devices all day, people can see whether or not they need to add more activity throughout the day. In fact, according to Porcari. Studies show that people are 30 to 40 percent more active when they use activity trackers.” So, perhaps the absolute accuracy of the device is less important than the fact that they do a good job of getting people up and moving.

And that, says Stackpool, is the take-home message for consumers: Do whatever it takes—whatever works for you—to be more active. If wearing an activity tracker helps you do that, your best bet is to choose a device based on comfort, ease of use and whatever additional features might appeal to you.