Why Fat Can Be A Factor In Elevated Glucose Levels
When we enjoy a dinner with high fat content, such as fettucini, buttery garlic bread, and a rich dessert, we might go to bed with our glucose level in target range, but wake up to a surprisingly high number.
The reason for the surprise may have nothing to do with the meal's high carb content. Fat is more metabolically active than once thought, and can contribute to glucose elevation in a couple ways.
Fats can raise blood sugar by increasing our level of free fatty acids, and by altering the absorption of glucose following a meal.
More FFAs
Eating a high fat meal raises the free fatty acids (FFAs) circulating in our bloodstream. This is not a problem if it occurs occasionally. However, having chronically high FFA levels from the regular consumption of high-fat meals is associated with insulin resistance in skeletal muscles, and in the liver.
When muscle and liver cells are insulin resistant it takes extra insulin from the pancreas, or from an injection, to transport glucose into cells from the bloodstream. If the extra insulin is not available, glucose levels will rise.
There is also some evidence that FFAs reduce the release of insulin by beta cells in the pancreas, but this mechanism is not well understood.
Slow Mover
Besides elevating FFAs, eating a high fat meal changes the timing of glucose absorption because fat digests slowly. It moves leisurely through the digestive tract, sometimes taking four to six hours for complete processing.
This is primarily an issue for those taking insulin since fast-acting insulins work in the body for three to four hours. After a fatty meal the insulin might become active before a substantial amount of glucose reaches the bloodstream, and may be finished working before all available glucose is processed.
This is why a glucose reading two hours post-meal may be on target, but five to six hours post-meal could be high.
Common Sense
Though high fat intake can affect blood sugar levels, fat should not be considered a villain. We need a certain amount of healthy fats daily to keep our body functioning optimally. Common sense tells us:
- Enjoying an occasional fatty meal is okay, but realize that consuming 40 grams or more of fat - especially a lot of saturated fat - may make glucose control more difficult.
- Those on oral diabetes medications should consider increasing physical activity following a high fat feast; individuals taking insulin may need to make dose and timing adjustments.
It can help to stop thinking of healthy eating as being a low-fat, or low-calorie affair. It’s really about giving our body plenty of fresh whole foods most of the time, and then adjusting for the effects of occasional high-carb, high-fat indulgences.
Source: Joslin Center
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