The findings of this study emphasize the connection between chronic high blood sugar levels and the body’s ability to adapt to aerobic exercise. Individuals with elevated blood sugar may find it challenging to enhance their peak oxygen consumption rate, which refers to the maximum amount of oxygen the body can utilize during intense exercise.
Prior studies conducted by this research group indicated that high blood sugar levels in mice hinder “aerobic adaptation.” To investigate further, they aimed to determine whether a ketogenic diet might help reverse this impairment in exercise-trained mice. The ketogenic diet is characterized by higher fat intake and reduced carbohydrates.
To explore their hypothesis, the researchers used both mice with induced high blood sugar and control mice. Some of the high-blood-sugar mice were placed on a ketogenic diet, while others continued on a traditional diet. The control mice maintained a regular dietary regimen as well.
The study involved monitoring the mice’s weight and blood sugar levels, with some undergoing exercise while others remained inactive. Researchers also studied the effects of reverting to a normal diet after following the ketogenic plan and observed a subset of sedentary mice that performed a single exercise session.
After the exercise training period, researchers assessed various factors including blood sugar levels, maximum exercise capacity, and body composition.
The findings revealed that mice with high blood sugar on the ketogenic diet exhibited normal blood sugar levels when compared to those on a traditional high-carbohydrate diet. Additionally, these mice demonstrated elevated blood ketones, indicating a shift towards fat as a primary energy source.
Comparing Exercise Among Keto Diet and Sedentary Mice
In terms of exercise training effects, all mice, regardless of their diet or blood sugar status, experienced improvements such as increased lean mass and lowered random blood sugar levels. However, sedentary mice on the ketogenic diet gained fat mass and saw increases in weight.
Mice that engaged in exercise training while following the ketogenic diet did not experience the peak oxygen consumption issues seen in high-blood-sugar mice on a conventional diet, which showed diminished improvements in this area.
Additionally, there were no observed complications with skeletal muscle remodeling in exercise-training mice on the ketogenic diet, a problem detected in normal diet high blood sugar mice.
The authors suggest that this improvement in skeletal muscle remodeling may explain the enhanced peak oxygen consumption, with further research indicating that ketones could facilitate this muscle adaptation.
However, exercise performance levels were similar across groups, potentially due to lower glycogen reserves in the ketogenic group, which affects carbohydrate storage within the body.
Mice on a ketogenic diet exhibited higher rates of fatty acid oxidation, which contributes to the breakdown of fatty acids. Exercising mice on the ketogenic diet utilized greater oxygen levels “during the first 10 minutes of maximal exercise testing.”
The results imply that the modifications in peak oxygen consumption resulting from the ketogenic diet and exercise training are distinct from fatty acid oxidation rates. Furthermore, sedentary mice on the ketogenic diet also demonstrated higher oxygen utilization and fatty acid oxidation during moderate exercise compared to their counterparts on a conventional diet. They also showed variations in certain substances, such as lactate levels.
In the skeletal muscles of mice on the ketogenic diet, glucose metabolism and transport were downregulated, whereas fatty acid metabolism and transport were upregulated. The researchers noted muscle adaptations that suggest significant changes in response to the ketogenic diet.
These adaptations may be the reason for the observed increase in fatty acid oxidation rates. Further changes in muscle
Researchers further assessed how the ketogenic diet and exercise impacted mice with normal blood sugar levels.
One prominent discovery was that the ketogenic diet did enhance peak oxygen consumption rate in sedentary mice, but not in those undergoing exercise training. The study indicated that switching back to carbohydrates for one week from the ketogenic diet significantly improved exercise performance, reducing the gap between VO2peak and performance in KETO-fed mice.
Study author Sarah Lessard, PhD, Associate Professor at the Fralin Biomedical Research Institute, noted to Medical News Today:
“When combined with exercise training, a keto diet can significantly enhance the health benefits derived from exercise in mice. Specifically, mice with hyperglycemia that followed a ketogenic diet showcased more significant improvements in aerobic exercise capacity (a measure of the body’s oxygen usage) than those on a regular high-carb diet.”
“We believe that the exercise-related improvements seen with the ketogenic diet might stem from its ability to lower blood glucose levels, as high blood glucose seems to hinder some of the positive impacts of exercise,” she added.
However, this study’s primary limitation is its reliance on male mice, which may not directly apply to humans. The researchers also utilized cell research, which poses additional challenges in translating conclusions to humans.
In the study, the high blood sugar levels were induced in mice, which varies from how diabetes develops in people. Moreover, the ketogenic diet administered to the mice may differ from typical human dietary practices.
Furthermore, the authors acknowledged that they did not measure the effects of the diets on fasting ketone levels or post-glucose-load insulin levels, which could have provided further insights. Although caloric intake was generally higher for mice on the ketogenic diet, exercise counterbalanced these increases.
It is also conceivable that fat mass could have influenced the peak oxygen consumption results.
Subsequent research should investigate the ketogenic diet’s effects in conjunction with exercise in people with elevated blood sugar and confirm the underlying biological mechanisms.
While the findings in this study were derived from mouse models and suggest a need for further investigation, they do indicate potential benefits of a ketogenic diet combined with exercise for individuals with diabetes. Lessard noted to Medical News Today:
“Individuals with elevated blood sugar due to diabetes or insulin resistance may not experience the same health benefits from exercise as those with normal blood sugar.”
“Our research indicates that dietary strategies or treatments aimed at lowering blood sugar in hyperglycemic individuals could enhance responses to exercise training, leading to improved aerobic capacity, which is critical as low aerobic fitness is a significant risk factor for chronic disease and mortality,” Lessard concluded.
While the ketogenic diet may present potential benefits, caution is advised. Karen Z. Berg, MS, RD, CDN, not part of the study, commented:
“A ketogenic diet consists of high protein and fat while limiting carbohydrates. Unfortunately, many individuals with hyperglycemia or Type 2 diabetes also deal with other health issues that may not align with a ketogenic approach. Often, Type 2 diabetes coexists with obesity or heart disease, making a high-fat diet unsuitable for these individuals.”
That being said, some individuals may benefit from the ketogenic approach. Kristin Kirkpatrick, MS, RDN, who also did not participate in the study, remarked:
“When considering keto research, we must align it with real-world applications. In my practice, I’ve noticed that both ketogenic and lower-carbohydrate methods can yield significant advantages, with ‘lower carb’ typically being around 25% of total caloric intake.”
“However, one of the fundamental questions surrounding a ketogenic diet is its sustainability. The long-term success of any diet ultimately hinges on an individual’s ability to adhere to it consistently.”
— Kristin Kirkpatrick, MS, RDN
