Last week we looked at the insulinemic response to sugars – ingestion of sugar causes insulin to be released into the bloodstream. Insulin controls the storage and release of free fatty acids in and out of fat cells . It does this through two mechanisms; when insulin is not present, the body stimulates the release of free fatty acids from the triglycerides (fat cells). When insulin is present, the body inhibits the release of FFA from TG and instead stimulates synthesis (building) of triglycerides.
Absence of insulin = body can use fat as fuel
Presence of insulin = body is switched to fat storing
This is why it’s important to know where (in your diet) sugars are coming from. An awareness about the types of foods that are high in sugar - including dairy and fruit, which most people may include as staple foods in a new diet plan (mainly because they are seen as 'healthy' food options). I'm not saying you should forever avoid these foods, or see them as poor choices, but with these foods, timing is everything, and awareness is your best friend. Here, we’ll go over how to best include these foods in your day, should you choose to eat them.
The Role of GLUT4
As mentioned in the last blog entry, dietary sugar is responsible for stimulating the release of insulin into the bloodstream and lowering your blood glucose level by quickly shuttling it into one of 3 places: the liver, muscle cells and adipose (fat) cells.
Insulin is the trigger which signals the GLUT4 (glucose transporter molecule 4) to travel from inside of these (liver, muscle, fat) cells, to the outer membrane of those cells. GLUT4 acts as a gateway/opening for the glucose to travel into these cells. So that's the downside? Well, when in a non-active or resting state, there aren’t too many GLUT4 cells that are signalled from within the muscle cells – so the glucose is most readily shuffled into the fat cells. The good news is that the translocation of GLUT4 in skeletal muscle cells is triggered by muscular contraction (i.e. exercise), which means we can pre-emptively flip the switch so that glucose is preferentially siphoned to the muscle cells rather than the fat cells.
"Exercise training is the most potent stimulus to increase skeletal muscle GLUT4 expression, an effect that may partly contribute to improved insulin action and glucose disposal and enhanced muscle glycogen storage following exercise training in health and disease."
Richter EA1, Hargreaves M.Journal Physiol Rev. 2013 Jul;93(3):993-1017. doi: 10.1152/physrev.00038.2012
So, long story short - if you chose to include foods in your diet that are high in sugar (fruits, grains, milk, etc.), timing is everything! Eat these foods during, or immediately following exercise and you can do so without sabotaging your weight loss goals. Knowledge is power in this case.
sugar + a current state of non-activity = glucose travelling preferentially into fat cells
sugar + a current state of exercise/post-exercise = glucose travelling preferentially into muscle cells
What's considered exercise? Well, basically it's sustained muscular contraction, so if you're someone who builds exercise into your daily routine, that's great. If you don't have the time, desire, or ability to fit it in, it can be as simple as doing a few short bodyweight exercises such as push-ups, squats, lunges, planks etc. Start with whatever you can do (this may just be 10 push-ups in the beginning), then as you become stronger, just increase the number of reps until you get to a mentally manageable number. Doing 2-3 minutes of exercise just 2-3 times per day can serve as a great catalyst for weight loss.
Next week’s blog will address refined grains