Grapefruit for Fat Loss

Grapefruit may play a minor role in weight loss, but doesn’t quite live up to its fat-burning legend.

• Enhanced metabolism. Grapefruits carry an abundance of the polyphenol, nootkatone, which may stimulate energy metabolism by activating AMPK.
• Increased glucose uptake. It’s a stretch, but this grapefruit bio-activity may help support the balanced blood sugar that’s associated with appetite control and weight management.
• Source of fiber. Grapefruit pith may serve as an excellent source of pectin fiber to help decrease appetite while increasing satiation.

Overview

The “forbidden fruit,” as described in Hughes’ The Natural History of Barbados (1750), is believed to have originated in Barbados as a natural genetic cross of sweet orange and pummelo, both of which were introduced from Asia in the 17th century.

Use of grapefruit (Citrus paradisi) as a dietary measure was first introduced by William H. Hay in the 1930’s due to its ostensible, and somewhat mythical, ability to burn fat. The grapefruit diet plan, revamped as the “Hollywood diet,” was decisively popularized in the 1970’s along with dozens of other diets during the American dietary craze. Declarations to the extent of: feel fat disappear and watch your waistline shrink in virtually days, toyed with unwitting enthusiasts’ desire to unearth that coveted slim body tone with the least amount of hassle.¹

Eating grapefruits supposedly triggered one’s body not only to instantly oxidize fat deposits and wash them out of the system, but reduce appetite as well. The strategy entailed consuming half a grapefruit before each meal for ten consecutive days, with meals consisting of low-carbohydrate, high-protein foods.

This concept of “10-days, 10-pounds off” offered a short-term, rapid weight loss, but at the cost of a dangerously insufficient intake of 800 calories a day. With no biochemical corroboration, however, the belief that grapefruit could serve as a catalyst to burn body fat rapidly came to a fizzle.

Research in recent years, however, points to several active ingredients found in grapefruits that play a recognizable role in lowering the BMI of obese persons:

• Nootkatone, an aromatic that decreases somatic fat ratio²
• Naringenin and Naringin, bioflavonoids that facilitate glucose metabolism³
• Pectin, a fibrous nutrient with dietary ramifications⁴

How Grapefruit Might Help With Fat Burning

Enhanced Metabolism

Grapefruits are like nutritional dynamites that are chock-full of healthy boosts, one of which is the compound nootkatone – a central activator of the AMPK signaling pathway. The significance of this finding stems from the understanding that AMPK manages the ever-complex metabolism system of the human body.⁵ A pre-clinical test that had nootkatone fed to mice, displayed grapefruits’ potential interactions with obesity.

• Modest weight loss and BMI reduction was noted in obese mice when fed nootkatone, and fat mass appeared to be reduced.⁶

Stimulation of Glucose Uptake

Two other health nuggets found in grapefruits are the bioflavonoids naringin and naringenin. Their interactions with glucose metabolism presented positive implications in several studies and are proven to be efficacious for the treatment of metabolic syndrome and obesity in animals.

• Naringin protected mice that were exposed to a high-fat diet through activation of AMPKα.⁷
• Naringenin battled high cholesterol and triglyceride levels in mice and may serve as a therapeutic strategy for hyperlipidemia.⁸

Note that effective doses still need to be established before using these bioflavonoids for clinical trials.

Supply of Fiber

Though not quite as tasty as the rest of the fruit, the pith of grapefruits is known to contain substantial amounts of pectin, which provides an excellent source of dietary fiber. Doses of pectin as small as 5 grams mixed with orange juice increased satiety in healthy U.S. adults and may facilitate weight loss.¹⁰

Grapefruit Reputation

According to certain factions, the “forbidden fruit” may prolong life by promoting cell growth and maturation through spermidine – found in ample quantities in grapefruits and human sperm.¹¹ Although the role of spermidine in the enhancement of human cell growth has been reported, a direct association between grapefruits and cell growth has yet to be identified and thus far hinges primarily on hearsay. Eating a lot of grapefruit and having a lot of sex is, nevertheless, not to be discouraged.

The grapefruit has further been repeatedly recommended as a fat burner, particularly alongside diet craze resurgences in the 30’s, again in the 70’s, throughout the 90’s, and quite nearly every other year since then.

Research

Animal Research

Nootkatone, as observed in one mouse study, was administered to obese mice at 200 mg/kg body weight in order to determine its impact on weight loss. By activating AMPK in skeletal muscle and the liver, nootkatone may aid in: 

• The prevention of obesity and hyperglycemia in obese mice, which had significant reductions in body weight gain, abdominal fat accumulation, and development of hyperglycemia, hyperinsulinemia, and hyperleptinemia, as well as a 21% improvement in endurance capacity.

Naringenin supplementation at 0.003, 0.006, and 0.012% in rats also demonstrated various positive upshots of eating grapefruit in another study. Through activating the PPARa transcription factor, naringenin may:

• Lower adiposity and triglyceride contents in adipose tissue.¹²

Grapefruit seed extractions, in the form of methanol, were fed to rats at 10 ml/kg of body weight/day in yet another study. Grapefruit in this form seems to:

• Reduce fasting blood glucose levels and induce weight loss in rats.¹³

Human Research

The grapefruit diet (one half of a grapefruit three times a day) may result in modest, although not scientifically significant, weight loss

Throughout the course of six weeks, 74 overweight or obese participants ate either one half of a Rio-Red grapefruit (whole fruit) or a randomized control diet with each meal after completing a three-week washout phase. Weight loss, waist circumference, blood pressure, and lipid content were compared.

• The study concluded that, although grapefruit consumers experienced modest weight loss (-0.61 ± 2.23 kg) and reduction in waist circumference (-2.45 ± 0.60 cm), “the diet does not significantly decrease body weight.”¹⁴

Eating one half of a grapefruit may trigger weight loss in obese patients

Metabolic syndrome parameters were compared among eating one half of a fresh grapefruit (127 g), grapefruit juice (237 mL), grapefruit capsules with apple juice, or placebo capsules with apple juice before each of three meals a day for a period of twelve weeks.

• Concluding measurements indicated that “half of a fresh grapefruit eaten before meals was associated with significant weight loss” in metabolic syndrome patients.¹⁵

Using a grapefruit preload (127 grams) before meals may contribute to weight loss

The twelve-week study examined the effects of eating, at 127 grams each, either one half of a grapefruit, grapefruit juice, or a water preload three times a day in a total of 85 obese men and women. The analysis was preceded by a two-week caloric restriction phase.

• Results demonstrated that “clinically significant weight loss can be achieved when consuming a low energy dense preload before meals.” It is important to note, however, that there were no observable differences among forms of the preload – be they whole grapefruit, grapefruit juice, or water.¹⁶

Grapefruit Dosage for Fat Burning

Grapefruit, like most everyday produce, is primarily consumed as a whole fruit. As such, specific serving sizes are difficult to identify to a tee. The most common dosages used:

• 127 grams of grapefruit three times a day
• Either as whole fruit (one half of a grapefruit), juice, or powdered as a capsule, each providing near identical quantities of essential bioflavonoids and aromatics

Additional components of the fruit may be ingested to positive effect with no known side effects: candied or juiced pith (5 g), which supplies pectin; seed extract concoction (150 mg) with prebiotic effects.

Grapefruit supplements:

• Grapefruit as a powdered supplement can be found in 500 mg capsules, equivalent to one half of a fresh grapefruit.
• Grapefruit pectin in 5 g doses as a candied fruit or in servings of 3 g when taken as a capsule provides a single gram of both dietary and soluble fiber.
• Grapefruit seed extracts supply between 100-200 mg  and may be taken in servings of 10-15 liquid drops in water three times daily.

Side Effects

The general consensus maintains that grapefruit is a healthy fruit with no known side effects when consumed at the recommended amount of 127 grams.

More on the subtle influences of social culture on nutrition.

Available Forms of Grapefruit

Grapefruit is most popularly eaten as a whole fruit snack or juice. Forms of dietary-correlated supplementation include:

• Whole Fruit. Frequently eaten in halves with added sugar either as a cold breakfast or as a warm evening snack. The same quantity may also be pulverized and taken as a capsule.
• Juice. Most often taken as standalone grapefruit juice but is known to be mixed with other substances for taste.
• Extract. Alcohol decoction of grapefruit seeds has been used in studies showing nutritional advantages. Check out other types of extracts.

References