Overweight people who are dieting and exercising more can increase their chances of success by making sure they consume enough vitamin C. A human study done at Arizona State University, soon to be published in Nutrition, suggests that vitamin C [structural formula shown here] makes physical exercise less tiring for fatties.
Physical exercise is heavier going for overweight people than for thin people. If you get a group of fat people and a group of thin people to do the same physical exertion, the fat people use more oxygen than the thin ones, and they report more fatigue afterwards too. [Int J Obes (Lond). 2006 Apr; 30(4): 652-60.] When both groups were told to exercise at an intensity that was 10 percent higher than the level they would choose themselves, the fat people gave up immediately. Which points to why people who want to lose weight and start exercising so often give up half way.
The researchers believe that this phenomenon is partly due to insufficient vitamin C intake. In developed countries vitamin C intake is alarmingly low – so low that doctors are starting to encounter cases of scurvy. A more modest vitamin C deficiency can also result in a decrease in L-carnitine production. Cells need this amino acid to burn fatty acids.
The researchers did an experiment with twenty obese test subjects. The subjects were put on a diet for four weeks – they were given 30 percent less energy than they burned daily. The diet provided 40 mg vitamin C per day. That’s too little, but not so little that you’ll become ill in the short term.
The experimental group were given a supplement containing 500 mg vitamin C. The control group were given a placebo.
Before starting on the diet, and at the end of the four weeks, the subjects had to walk at a stiff pace for sixty minutes on a treadmill. They exercised at 50 percent intensity of their VO2max.
The vitamin C supplement had no effect on their fat burning [RER], but after the four weeks the Ratings of Perceived Exertion [RPE] and the POMS fatigue score after exercising were 10 and 55 percent lower respectively in the experimental group. The scores in the control group were respectively 1 and 33 percent higher.
“The noted decreases in heart rate and perceived exertion during exercise and fatigue in general in the Vitamin C participants compared with the control participants are noteworthy and deserve further investigation”, the researchers write. “Vitamin C supplementation would represent a simple treatment to decrease fatigue and improve adherence to weight-loss diets.”