Studies have shown that raspberry ketones hold promise for fat loss. In one study mice were fed a calorie rich high-fat diet supplemented with raspberry ketones. After 10 weeks it was shown that the raspberry ketone supplementation prevented both subcutaneous and abdominal (visceral) fat gain, and also protected against development of fatty liver 3. These anti-obesity effects are beneficial, since abdominal fat (the type of fat that causes protruding bellies even in otherwise "skinny" people) is strongly associated with obesity-related complications like the metabolic syndrome, Type 2 diabetes and coronary artery disease, even in the absence of classical risk factors 4,5. The association between abdominal adiposity and accelerated atherosclerosis has been shown to be independent of age, overall obesity or the amount of subcutaneous fat 5. Thus, raspberry ketones can help you get in better shape and improve your health.
Raspberry ketones appear to stimulate fat loss several ways:
1. Increasing liberation of fat from fat stores (a process called lipolysis) 3,6.
2. Enhancing energy expenditure by activating thermogenesis (heat production) in brown adipose tissue (also known as BAT, see below) 3.
3. Increasing fat burning (fat oxidation) 3,6.
4. Increasing levels of the hormone adiponectin 6.
5. Suppress fat synthesis from fructose (sugar) overfeeding 3, and inhibit fat accumulation 6.
6. Inhibit fat absorption 3.
The effect of raspberry ketones on BAT and adiponectin are especially interesting.
Brown Adipose Tissue, also known as BAT, is a special type of fat tissue that produces heat instead of storing fat7. It was previously thought that BAT was only present in significant amounts in rodent, and infants 8. However, recently has been shown that even adult humans have metabolically active BAT depots 9,10, that can be induced and stimulated7. This has put BAT in the spotlight of obesity research 8-11; thus, we are most likely going to hear a lot about BAT -in the near future. Bearing this in mind, it is interesting that raspberry ketones stimulate BAT induced increases in energy expenditure. The more you can increase your ability to burn off excess calories (by raising your energy expenditure), the better are your odds of shedding those unwanted pounds of fat.
Fat cells are often regarded as calorie storing depots. However, fat cells also secrete several substances hormones, both good and bad (depending on the location of the fat depots) 12-17. One of the good hormones secreted from fat cells is adiponectin 18-21. Adiponectin is a relatively newly discovered adipose tissue derived hormone that circulates in the blood at high levels 22, and has multiple health promoting effects.
Adiponectin enhances insulin sensitivity, lowers blood glucose (blood sugar) and reduces triglyceride levels 22-24, in addition to boosting fat burning 25. Apart from its anti-diabetic, anti-hypertensive and anti-atherogenic properties, recent studies have revealed that adiponectin also has anti-inflammatory and anti-cancer functions 19-21,26,27. Actually, one mechanism by which abdominal fat causes metabolic and cardiovascular diseases is via a reduction in adiponectin levels 26. Low levels of adiponectin contribute to the development of insulin resistance, type 2 diabetes and cardiovascular diseases in obese or overweight people 18,22. Adiponectin levels are inversely related to the degree of adiposity 23, which means that the lower the adiponectin levels, the more fat we're likely to be carrying around.
It is interesting that exercise, which is well known for all its beneficial health effects, also increases adiponectin levels 28. The importance of adiponectin is further underscored by proposals to make it a biomarker for different health conditions, and a therapeutic target for health promotion interventions 21. It has further been speculated that adiponectin - or interventions that stimulate adiponectin secretion or action - might play a role in the therapeutic armament against disease states associated with insulin resistance, mainly type 2 diabetes mellitus and obesity 29. Thus, the ability of raspberry ketones to increase adiponectin secretion undoubtedly contributes to the anti-obesity and health promoting effect.