Is it really okay to have milk in your coffee when fasting?
Proponents of time-restricted eating can’t agree on whether it’s okay to have milk in your coffee during intermittent fasting – so we asked the experts.
It’s hands-down one of the hardest things about intermittent fasting if you’re doing the 16:8 or a similar regime of time-restricted eating: trying to get used to black coffee or tea in the morning if it’s just not your thing.
I don’t know about you, but I really don’t like black coffee, and at 7 o’clock in the morning, facing another five hours without my morning coffee with milk just makes me want to throw in the towel.
I have keenly engaged with the “cheat theories” that abound. “Dirty fasting” is a thing, with proponents alleging that if you consume a small amount of calories in your fasting window – in the order of less than 100 – you will still reap many of the benefits of intermittent fasting, in particular weight loss.
Then there are those who say consuming 50 calories or less is totally okay during a fasting window, so don’t worry a jot about that bit of milk in your coffee.
Even the guru of the 5:2 diet, Michael Mosley, has stated that a little milk in your coffee is totally fine.
But is it really?
To answer the question, we need to consider the science of what happens within your body when you fast, and you also need to consider your particular goals and the reasons that you choose to fast.
Generally, the goal of intermittent fasting is to enter a state in which the body is deprived of glucose and is forced to rely on alternative methods of energy metabolism, drawing upon glycogen, lipids, and amino acids. During the fasting state, insulin levels drop very low and you want to keep them low because insulin, which is released by the pancreas in response to glucose being released into the bloodstream following the ingestion of any food, stimulates the uptake of glucose into cells, giving them an energy source – exactly what your fast was designed to deprive them of.
There’s no doubt that having a bit of milk in your coffee will kick off this process of glucose being released into the bloodstream and subsequently spiking your insulin levels. This is especially so because milk is fairly high in natural sugars and carbohydrates.
“Definitely you are you are increasing your glucose and you are increasing your insulin,” says Professor Luigi Fontana, scientific director at the University of Sydney’s Charles Perkins Centre. “As soon as the cells of the pancreas are sensing this increase in glucose, they are going to produce insulin, there is no doubt about. How much depends on how much milk you’re consuming.
“Insulin basically is a powerful hormone that, among many other things, is increasing the deposition of fat in adipose tissues. What insulin does is to push glucose into skeletal muscle cells to become glycogen, or to become ATP if you’re exercising, or to push fat into adipose tissue to be stored.”
Professor Fontana is a hard no on drinking any milk at all during the fasting state, if you’re really trying to stay in ketosis and force your body to burn fat for fuel.
But he does acknowledge that the whole equation depends on quantity – and that’s the argument made by dietitians such as Camilla Dahl, who says it’s unhelpful to take an entirely purist attitude to fasting.
Ms Dahl advises those who really can’t get used to black coffee to allow themselves to have a little milk – but no more than two tablespoons.
“It will have an effect on glucose and insulin, but it’s such a small amount that it’s just like a little blip and you’ll go back into the fasting state really quickly,” she says.
“But if you go and have a latte it won’t be a blip, it will be a big mountain.”
Ms Dahl has one surprising tip for those who like a milky coffee – she suggests that instead of milk, put one or a maximum of two tablespoons of cream into your brew.
“Cream is pure fat, so the body doesn’t have an insulin response to it at all,” Ms Dahl says.
“I think having a coffee with cream or a tiny bit of milk makes it a lot more palatable for a lot of people, and overall makes fasting more tolerable.”