The ‘no carbs should pass your lips after 5pm’ advice has become weight loss gospel over the last decade – but is it diet fact or fiction?
What’s fascinating about this study – looking at a group of overweight policemen and women in Tel Aviv - was its finding that when these people ate most of their daily carbs with dinner rather than spreading them more evenly during the day it had a positive effect on levels of leptin – the hormone that lets us know when we’re full.
“When people lose weight, their leptin levels fall and because this can make them feel hungrier, it can sabotage their efforts to keep losing weight,” Barclay explains. But this research found that the people who ate carbohydrates mostly at dinner had higher levels of leptin than those who ate carbs mostly during the day. Their levels of blood glucose, cholesterol and insulin also improved.
“This is quite a good study so I think it helps debunk the ‘no carbs after 5pm’ theory,” he says.
The idea for the research stemmed from earlier studies on Muslims during Ramadan which showed that fasting during the day and then eating high carbohydrate meals in the evening could also influence levels of leptin.
As for the origins of the evening curfew on carbs for weight loss, that’s lost in the mist of diet folklore, but Barclay thinks it evolved from the low carb message of the born again Atkins Diet of the late 90s.
There’s no weight loss magic attached to stripping carbs off the plate at dinner other than reducing the number of kilojoules you eat – but common sense tells you that this can backfire if you’re left feeling so hungry that’s it hard not to keep grazing for the rest of the evening.
Not that loading up on refined starchy or sugary carbs in the evening is a good idea either - they don’t fill you up and they can add extra kilojoules without delivering much in the way of nutrients. But a moderate amount of quality carbs can help keep hunger pangs under control as well as adding nutrients and fibre, says Alan Barclay.
He suggests whole grains or carbohydrates with a low to medium GI rating – brown basmati rice, Doongara rice, real sourdough bread, legumes, orange sweet potato, Carisma potato, sweet corn, bulgur and quinoa are some of them. Including carbohydrates like these is also important if you’re physically active, he adds.
Another argument for not short changing yourself on carbs at night could be the effect they might have on sleep.
Lack of sleep can make it harder to stick to a healthy weight. It’s not only an energy sapper that derails good intentions to get more exercise but there’s growing evidence that it can disrupt the hormones that control hunger, increasing our urge to eat.
Carbohydrates can play a role in helping us get to sleep because they increase the brain’s uptake of an amino acid called tryptophan which in turn produces serotonin that’s important for sleep, Barclay explains.
Some proteins also help with production of tryptophan which is why the old wisdom of warm milk at bedtime still holds true, he adds – dairy products combine both carbohydrate and protein.