We’re all aware that a nutritious diet and exercise are vital components of a healthy lifestyle. You can benefit from one without the other, but you’ll get the best results by combining them. Modern research is demonstrating that the manner in which we incorporate these two elements into our lives can have a powerful impact on the results. Today’s blog looks at a simple strategy that may help you to burn more fat, improve your work-outs and curb your appetite.

Reaching New Heights By Eating Low

A common question for most exercisers is what to eat prior to a work-out. A new study in the Journal of Nutrition offers a scientifically based answer. The British scientists involved in this experiment provided a group of 8 sedentary women with one of two types of breakfasts: 1) a low glycemic meal (LGI); or 2) a high glycemic meal (HGI). The lower the glycemic content of a meal, the smaller the anticipated blood sugar response.

On separate days the volunteers consumed either an HGI or LGI breakfast. Three hours later, they engaged in a 60 minute walking session. Blood tests were taken in order to compare any changes that occurred in the metabolism of the walkers. Here’s an overview of the results:

• Blood sugar levels rose to a greater extent when the participants were given the high glycemic meals.
• 2 hours after eating the low glycemic meals, there was an increase in the level of fat burning (as measured by PFFAs – plasma free fatty acids).
• Both groups exhibited signs of fat burning during exercise, but those consuming the LGI breakfasts burned more fat.
• The authors of the study also noted that those consuming the LGI breakfasts felt more satisfied (ie, less hungry) later in the day after eating a prescribed lunch.

The conclusion of this trial was summarized as such, “consuming a LGI breakfast increases fat oxidation during subsequent exercise and improved satiety during recovery in sedentary females. As such, individuals trying to shed fat may consider choosing LGI foods eaten prior to when they exercise.”

Another recent experiment found similar results in women who regularly exercise. This is an important distinction because we need to understand if diet plays a different role in those who are very active as compared to those who are infrequent exercisers.

A 2006 trial again tested the effects of a low vs high glycemic meal prior to an intense 60 minute treadmill work-out. The LGI meal had a glycemic index of 44. The HGI menu registered at 78 on the glycemic index. Please refer to the glycemic index/load chart for more information.

As in the previous trial, blood sugar levels were higher when the HGI meals were consumed. In this experiment, they also measured insulin response and found it was elevated more so by meals with a higher glycemic index. In addition, female participants burned a significantly larger amount of fat when they ate a LGI meal prior to exercising.

Are the results the same in the male population? It appears so. Here’s a brief analysis of two recent studies that help to clarify the role of gender in the diet/fat burning connection:

• In 2006, a trial was published in the International Journal of Sport Nutrition and Exercise Metabolism. Eight male “recreational runners” were given an almost identical test as the two previous studies conducted on female volunteers. After a 12 hour fast, they were first given an LGI breakfast. Then they engaged in a vigorous running session until they reached the point of exhaustion. Seven days later, they repeated the experiment, but were fed an HGI breakfast prior to running.
• The results indicate that the male athletes ran longer and burned more fat after eating the LGI meal. The researchers also found that they burned more fat while at rest, after consuming the LGI meal.
• A year prior to that, a trial was conducted on 9 men to see if there was a relationship between the types of carbohydrates consumed and exercise performance. In this experiment, the LGI or HGI meals were given after strenuous exercise. The goal was to determine which type of meal would help the men recover better and perform more efficiently in a follow-up work-out session. The men on the LGI diet exhibited a greater capacity for endurance and burning fat (fat oxidation) as compared to those on the HGI diet.

The final issue I’d like to address is that of long distance, endurance athletes. Many people assume that larger amounts of high glycemic carbohydrates (“simple carbs”) are needed for optimum performance during these types of activities. However, this is not the case for everyone. I know of at least one gentleman who competes in marathons while maintaining a strict, low-carbohydrate diet. But that’s just an anecdote. Here’s some scientific evidence that I found from September 2008.

A study, based at The Chinese University of Hong Kong, determined that there was no statistical difference in the performance of runners asked to run a 21 kilometer distance after consuming either a HGI or LGI meal. However, there was a reduction in cortisol (a stress hormone) and an improvement in recovery in those ingesting the LGI meal. These two changes may affect longer term exercise performance, the likelihood of injury and resistance to exercise related illness.

On a personal note I can tell you that I’m currently working out harder than I have in many years. I’m presently on a low glycemic/lower carbohydrate diet, in which I make no effort to increase my carbohydrate consumption around the time that I exercise and it works perfectly fine for me.

Be well!

JP