Green tea latte or espresso latte?

My friend Kathy, who reads this blog, sent me a diet question a few weeks ago. I thought I'd post the question and my reply here.

Kathy asked: Which drink is better at Starbucks: A tall non-fat green tea latte, or a double tall non-fat espresso latte?

The green-tea latte breaks down like this:

130 calories
27 g carbs (26 of sugar)
6 g protein
0 g fat

The espresso latte* breaks down like this:
114 calories
18 g carbs (16 of sugar)
11 g protein
0 g fat

* Starbucks doesn't provide info for a double latte; to get the exact breakdown, I subtracted the data for one ounce of milk and replaced it with one ounce of espresso, the typical size of a shot.

So, assuming the caffeine content is the same (I have absolutely no idea if it is, but Kathy's friend told her it was; she had switched to green tea lattes thinking it was healthier, then learned it may not be), the choice is the espresso latte.

Now, obviously there's a 16 calorie difference here. But that's not really the reason why the espresso latte is better. You can burn 16 calories by parking further away at the grocery store or taking the stairs instead of the elevator. (Of course, if you always add 16 calories to what you're eating, eventually it adds up - but pretty much it's negligible for most people.)

The espresso latte is better because of the source of the calories. There are almost twice as many calories from protein in the espresso latte, and more than one-third fewer calories from sugar. Sure, I know that the way to lose weight is to consume fewer calories than you burn - and that's regardless of the source of those calories - but you also have to take into account the effect the calories will have on your body.

Carbohydrates spike your blood sugar. Your body produces insulin in response to it, and your blood sugar drops. This is why you feel a surge of energy from sugar, but then you crash. I know a lot of people here at work who operate on this cycle: go to the kitchen. Get a Coke. Drink it. Go back to the office. Code for half an hour. Return to the kitchen, feeling hungry. Find a cookie. Eat. Return to coding. It's interval training for weight gain!

But there's a fine line to walk here. Our bodies need carbohydrates - the brain needs sugar to operate! (Trust me on this one. I've seen my poor diabetic husband have hypoglycemic seizures due to low blood sugar. Not pretty.) So to stave off that feeling of hunger, we can combine carbohydrates with protein and fat.

Both protein and fats have a longer cycle - you don't peak, because they don't really raise your blood sugar, and your body takes longer to process them. So even after the carb rush has come and gone, protein and fat stay in your system and keep you satiated.

I have a rule: no carbs without protein. That even goes for the worst-possible carbs - banana bread, cake, ice cream, etc. It really helps to stop the sugar high/sugar crash cycle. It may seem somewhat counter-intuitive - I eat EXTRA calories when I eat the bad calories - but it's to prevent me from feeling starving an hour later and saying something like, "Hey. I ate ice cream today. The day is ruined. Might as well eat a brownie now!"

(Which everyone who knows me knows I actually have said before, but presumably less often than I would have had I not had the carbs + protein rule.)

So honestly, the best possible thing for Kathy to do with her espresso latte might even be to not do the non-fat milk thing and instead go for 1%. That way she gets a little more fat for just a few more calories, and she'll be even less likely to crash and need more sugar. Plus, it tastes better!