Blackberry intake, fat burning and insulin in overweight men
What it found
In overweight and obese men, eating 600 g of blackberries a day for a week increased fat burning and lowered insulin levels after a meal.
Blood sugar responses were about the same with blackberries and the gelatin control.
What they found
Studies in people
Fat burning over 24 hours
Average 24-hour respiratory quotient was lower with blackberries (0.810) than with gelatin (0.817), which indicates more fat oxidation. This corresponded to a 7% increase in 24-hour fat oxidation (141 g/day with blackberries vs 132 g/day with gelatin).
Fat burning at meals and exercise
Respiratory quotient was lower with blackberries in the evening, morning and during exercise. Fat oxidation was 14% higher in the evening (28 g vs 25 g), 11% higher in the morning (21 g vs 19 g) and 12% higher during exercise (9 g vs 8 g).
Blood sugar after a meal
The glucose response during the meal-based glucose tolerance test was not significantly different between blackberries and gelatin (3488 vs 4070 mg·min/dL).
Insulin after a meal
Insulin response was significantly lower with blackberries than with gelatin (6485 vs 8245 µU·min/mL). HOMA-IR, a measure of insulin resistance, also improved with blackberries.
Free fatty acids
Serum non-esterified fatty acid levels during the meal test were higher on average with blackberries (48 meq·min/L) than with gelatin (39 meq·min/L).
Energy expenditure
Twenty-four hour energy expenditure was very similar between the two treatments (2485 vs 2439 kcals).
What the authors conclude
“Blackberry consumption may promote increased fat oxidation and improved insulin sensitivity in overweight or obese males fed a high fat diet.”
Also in their conclusions
- They conclude that blackberry feeding significantly increased fat oxidation and insulin sensitivity in overweight or obese men fed a high-fat diet including 600 g blackberries per day for one week compared to an energy matched control.
- They say this study offers translation of the anti-obesity effects of berries observed in rodent models to humans.
- They advise that further studies will be useful to clarify the findings and potential mechanisms of action.
How it was done
Berries and other anthocyanin-rich foods have prevented weight gain and excess body fat in rodents, possibly by changing which fuels the body burns. The authors wanted to see whether this effect also happens in people.
Twenty-seven overweight or obese men took part in a randomised, placebo-controlled crossover study with two treatment periods. For seven days they ate a controlled high-fat diet (40% of energy from fat) that included either 600 g of blackberries a day or a calorie and carbohydrate matched amount of gelatin, separated by a seven-day washout. On day 7 they spent 24 hours in a room-sized calorimeter and had a meal-based glucose tolerance test.
What it can’t tell you
- The study was in overweight or obese men only, so the results may not apply to women or to people of other body weights.
- The treatment could not be blinded because whole foods were used, which may affect how participants reported or behaved.
- The study lasted only one week, so it cannot show what happens with longer-term blackberry intake.
Who paid
- Conflicts
- The authors declare no conflict of interest.
- Authors work at
- Beltsville Human Nutrition Research Center, USA; University of Maryland, USA; Purdue University, USA
The paper
- Title
- Blackberry Feeding Increases Fat Oxidation and Improves Insulin Sensitivity in Overweight and Obese Males
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Licence
- CC BY. Words in quotation marks are the authors’; the rest is our summary.
- Cite
- Solverson PM, Rumpler WV, Leger JL, et al (2018). Blackberry Feeding Increases Fat Oxidation and Improves Insulin Sensitivity in Overweight and Obese Males. Nutrients. doi:10.3390/nu10081048Free full textPubMed 30096878DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error