Maybe you've heard the claim that raspberry ketone supplements can melt away fat and prevent weight gain -- even if your diet is high in fat. But what are they, and can they really do that? Medically Reviewed by Christine Mikstas, RD, LD on December 24, 2024, this article examines the existing research to determine if raspberry ketones live up to the hype as a weight loss aid.
What are Raspberry Ketones?
Raspberry ketones are natural chemicals that give red raspberries their enticing aroma. This substance is also found in small amounts in other fruits and berries, such as blackberries, cranberries, and kiwis. When ketones are taken from raspberries, they can be used to add fragrance and flavor to things such as colas, ice cream, and cosmetics. Raspberry ketone is a natural substance that gives red raspberries their powerful aroma.
Raspberry Ketones and Weight Loss: The Claims
Raspberry ketones are claimed to cause the fat within cells to be broken down more effectively, helping your body burn fat faster. They are also claimed to increase levels of adiponectin, a hormone that helps to regulate metabolism.
Examining the Evidence: Scientific Studies and Research
Despite the buzz surrounding raspberry ketones, the scientific evidence supporting their effectiveness as a weight loss supplement is limited and, in some cases, flawed.
Limited Human Studies
To date, only one small clinical trial of raspberry ketone has been conducted. Its results were published in two papers and suggest that daily supplementation with raspberry ketone improved biomarkers of oxidative stress and HDL, but not total cholesterol, LDL, triglycerides, blood glucose, liver enzymes, or body weight in 20 women with obesity. However, these findings have a high risk of bias due to several important methodological limitations. These include the lack of preregistration, double-blinding (to keep investigators from knowing which treatment group the participants were randomized to), and a power calculation (to justify the small number of included participants, 20). This limits the reliability of the findings. It should also be noted that these two papers were submitted, accepted, and published on the same dates, do not have a DOI number (a digital identifier that is necessary for a journal’s database indexing), and do not report any funding sources.
Read also: Exploring the health aspects of Diet Raspberry Ginger Ale
Studies on Mice and Rats
Raspberry ketone supplements exhibit promise in studies on mice and rats.
In one study, raspberry ketones were given to some mice fed a fattening diet. The mice in the raspberry ketone group weighed 50 grams at the end of the study, while the mice that didn’t get ketones weighed 55 grams - a 10% difference. Note that the mice fed ketones did not lose weight - they just gained less than others.
In another study in 40 rats, raspberry ketones increased adiponectin levels and protected against fatty liver disease. However, the study used excessive dosages. You would have to take 100 times the recommended amount in order to reach the equivalent dose. A dosage this severe is never advisable.
Multi-Ingredient Studies
Some studies have investigated multi-ingredient supplements that contain raspberry ketone along with several other ingredients, but specific effects of raspberry ketone cannot be determined from such research.
One such study, an eight-week trial, involved people cutting calories and exercising while taking a supplement containing caffeine, raspberry ketones, garlic, capsaicin, ginger, and synephrine. Those who took the supplement lost 7.8% of their fat mass, while the placebo group lost only 2.8%. However, the raspberry ketones may have had nothing to do with the observed weight loss. The caffeine or any of the other ingredients could be responsible.
Read also: Guilt-Free Raspberry Treat
Adiponectin and Metabolism
Adiponectin is released by fat cells and may play a role in regulating metabolism and blood sugar levels. People with normal weight have much higher levels of adiponectin than those who are overweight. Levels of this hormone increase when people lose weight. Studies demonstrate that people with low adiponectin levels are at a higher risk of obesity, type 2 diabetes, fatty liver disease and even heart disease.
However, even if raspberry ketones raise adiponectin in isolated fat cells from mice, this does not mean that the same effect will occur in a living organism. Keep in mind that there are natural ways to increase adiponectin that do not involve raspberry ketones. For example, exercise can increase adiponectin levels by 260% in as little as one week. Drinking coffee is also linked to higher levels.
Resemblance to Stimulants
The fact that raspberry ketones chemically resemble other stimulants suggests the potential for certain side effects. And there are anecdotal reports of jitteriness, increased blood pressure, and rapid heartbeat among people taking raspberry ketone supplements.
Dosage and Safety
Raspberry ketones in food and cosmetics are generally considered safe. But no one knows what short- or long-term effect raspberry ketone supplements could have on your overall health. No study has been done to document potential side effects. There are also no studies that look at potential drug or food interactions.
Synthetic Production
Even though the word “raspberry” may appeal to people, the supplement is not derived from raspberries. Extracting raspberry ketones from raspberries is extraordinarily expensive because you need 90 pounds (41 kg) of raspberries to get a single dose. In fact, 2.2 pounds (1 kg) of whole raspberries only contains 1-4 mg of raspberry ketones. That’s 0.0001-0.0004% of the total weight. The raspberry ketones you find in supplements are synthetically manufactured and are not natural.
Read also: Decadent Keto Dessert
METABO Study: A Closer Look
One study aimed to determine the safety and efficacy of METABO as an adjunct to an 8-week weight loss program. The placebo consisted of rice flour while the main ingredients of the METABO formula included raspberry ketone, caffeine, capsaicin, garlic organosulfur compounds, gingerols, shogaols, Citrus aurantium and related alkaloids, B vitamins, and chromium.
Experimental Design
The study utilized a randomized, placebo-controlled, parallel-group, double-blind design. Subjects were matched according to sex and BMI prior to being randomized into placebo or METABO groups. The study intervention included an 8-week diet and exercise program consisting of recreationally active men and women, randomly assigned to receive either a placebo or the manufacturer recommended dosage of their respective supplement (two capsules with breakfast and two capsules with lunch).
Diet and Exercise Program
Prior to starting the study, a state-licensed, registered dietitian designed a target diet to provide approximately 500 kilocalories per day less than each subject’s estimated daily caloric requirement as estimated by the Mifflin-St. Jeor equation x an activity factor of 1.2. Each subject was given seven days of menus based off their daily allowance for calories. All menus consisted of three meals and two snacks and targeted a 40% carbohydrate, 30% protein and 30% fat eating plan. Subjects performed three, 60-minute exercise sessions per week using a ‘boot camp’ type of training.
Measurements
All subjects had measurements of their weight, BMI, waist and hip girths, body fat and lean mass taken at week 0 (baseline), week 4 (midpoint of the study) and week 8 (end of the study). Blood samples were drawn at week 0 and week 8 for standard assessment of clinical laboratory parameters and at weeks 0, 4 and 8 for serum concentrations of adipocytokines (adiponectin, resistin, leptin, tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6)). Vital signs, including blood pressure and heart rate, were also recorded at weeks 0, 4 and 8.
Results
Of the 45 subjects who completed the study, significant differences were observed in: body weight (METABO -2.0% vs. placebo -0.5%, P < 0.01), fat mass (METABO -7.8 vs. placebo -2.8%, P < 0.001), lean mass (METABO +3.4% vs. placebo +0.8%, P < 0.03), waist girth (METABO -2.0% vs. placebo -0.2%, P < 0.0007), hip girth (METABO -1.7% vs. placebo -0.4%, P < 0.003), and energy levels per anchored visual analogue scale (VAS) (METABO +29.3% vs. placebo +5.1%, P < 0.04). During the first 4 weeks, effects/trends for maintaining elevated serum leptin (P < 0.03) and decreased serum resistin (P < 0.08) in the METABO group vs. placebo were also observed. No changes in systemic hemodynamics, clinical blood chemistries, adverse events, or dietary intake were noted between groups.
Conclusions
METABO administration is a safe and effective adjunct to an eight-week diet and exercise weight loss program by augmenting improvements in body composition, waist and hip girth. Adherence to the eight-week weight loss program also led to beneficial changes in body fat in placebo.
Alternative Methods for Weight Loss
Alternative methods to aid weight loss include meal replacement preparations, and nutritional supplements such as vitamins, mineral, and botanicals.
Other Potential Benefits
One study links raspberry ketones to cosmetic benefits. When administered topically as part of a cream, raspberry ketones appear to increase hair growth in people with hair loss. It may also improve skin elasticity in healthy women. However, this study was small and had a number of flaws.
The Obesity Epidemic
If you need to lose weight, you are not alone. More than a third of Americans are overweight - and another third are obese (1). Only 30% of people are at a healthy weight. The problem is, conventional weight loss methods are so difficult that an estimated 85% of people do not succeed (2). However, many products are advertised to aid weight loss. Certain herbs, shakes and pills are supposed to help you burn fat or reduce your appetite.
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