How a particular food affects your blood glucose has to do in part with the combination of carbohydrate, protein, and fat in the meal. However, you may have higher blood sugar levels after you eat a meal high in fat than if you eat a meal high in carbohydrates.

The conversion of foods into blood sugars

The foods you eat contain different amounts and combinations of carbohydrates, protein and fat. This is the portion of carbohydrates, protein and fat that is converted into glucose:

  • All digestible carbohydrates in your meal (fibre is considered a carbohydrate but is not digestible) convert to glucose
  • Half of the protein in your meal converts to glucose
  • 10 per cent of the fat in your meal converts to glucose

The peak effect of foods on blood sugars

Carbohydrates, protein, and fat show their peak effect on blood glucose at different times after a meal. Here is a guide:

  • Carbohydrates without fibre – Peak 15 to 30 minutes after a meal
  • Carbohydrates that contain fibre – Peak 1 to 1 ½ hour after the meal
  • Protein – Peaks 3 to 4 hours after the meal
  • Fat – Peaks 3 hours after the meal

Other factors that affect blood sugars

How foods affect your blood sugars has to do also with:

The amount of carbohydrate, protein, and fat in the meal
The size of the portion you eat
Whether the food is cooked or raw
Your blood glucose levels before the meal

However, people respond differently to carbohydrates and the same type of meal eaten by different people might have different effects on their blood glucose levels.

Foods that encourage high blood sugars

In this list you may find foods that may surprise you:

  1. Granola cereal
  2. Pizza
  3. Pasta
  4. High animal protein and fat meals
  5. Fried foods such as fried chicken and French fries
  6. Bagels eaten plain
  7. Chinese food in general, chow mein in particular)
  8. Ramen noodles

Are you having high blood sugars after high-fat meals?

Some people seem to have high blood sugars after meals high in animal fats such as bacon and eggs or pizza topped with sausage and pepperoni. It seems that in some people, insulin becomes less effective (insulin resistance) after meals high in animal fat. This can bring on high blood sugar levels.

If you have noticed this happens to you, try having smaller portions of the fatty foods and add some plant foods such as fruits, vegetables, and grains, especially those rich in soluble fiber and see if it makes a difference. Foods that seem to help minimize high blood sugars are:

  1. A green salad with kidney beans
  2. A cup of vegetable soup or bean soup
  3. A small serving of oat bran or oatmeal before a breakfast that includes high-fat foods
  4. Vegetables, high in soluble fibre such as artichokes, celery, sweet potato, Brussel sprouts, cabbage, broccoli, carrots, green beans, cauliflower, asparagus, and turnips.
    Nuts, soy foods
  5. Olive and canola oil
  6. Flaxseed
  7. Avocados

The only way to know for sure how your blood sugar responds to a particular meal is to test your blood sugar before you eat and two hours after the meal.

What percentage of carbohydrates, fat, and protein?

You probably have asked yourself more than once what is the correct percentage of carbohydrates, fat, and protein you should have in your meal to avoid high blood sugar levels. Here is some guidance:

One-third of the people with type 2 diabetes tend to do better when they include 35 to 40 per cent calories from fat, mainly unsaturated fat.

Two-thirds of the people with diabetes type II tend to fair best with a meal that includes 25 to 30 per cent calories from fat.

People whose insulin seems to be less effective after a high saturated animal fat meal (which seems to include Asians, Pacific Islanders, and African Americans) tend to do better eating a meal high in carbohydrates. Including foods rich in soluble fibre helps many people tolerate a meal higher in carbohydrates.

What about wine?

A glass of red wine with dinner does seem to encourage lower blood sugars for some people, but for others, the same glass of wine may have the opposite effect and their blood sugar may go up later that night.

Sweeter wines are the most dangerous because they tend to trigger higher blood sugars. You may do better with red and dry wines.

Final word

Although you may feel it is hard to predict what your blood sugar may do after a meal, it is not. If you test your blood sugar before and after meals for a while, you will become familiar with the foods and combinations of foods that affect your blood glucose the most.

That will provide you with a good guideline to keep your blood sugar under control. Keep in mind that your main goal, if you are diabetic, is to keep your blood sugars as close to normal levels as you can.


I am Andy Carpenter and I would start by saying that I have a Bachelor Degree in Nutrition Science conferred by California State University, Los Angeles and that I am certified as a Registered Dietitian.

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