Does Insulin Make You Fat? What Actually Matters

The short answer

Not on its own. Insulin helps store energy, but your body only stores fat over time when you eat more than you burn. That said, insulin is worth caring about for a different reason: lots of men over 40 with a belly have become less sensitive to it, and that’s a health issue. The good news is the fixes are simple. Lose some fat, lift weights, walk after meals, sleep better and eat protein first.

What does insulin actually do?

Insulin is like a delivery driver. When you eat, especially carbs, sugar rises in your blood. Insulin drives it to where it’s needed: your muscles, your liver, and yes, your fat cells.

It also tells your body “we’ve got food coming in, no need to burn stored fat right now”. That’s where the idea comes from that insulin makes you fat. It’s half true. In the hours after a meal, you store a bit. Between meals and overnight, you burn a bit. What decides your body fat over weeks and months is the balance of those two, and that comes back to total calories.

Where did the “insulin makes you fat” idea come from?

It’s called the carbohydrate insulin model. The idea is that carbs push insulin up, insulin locks fat away, and you get hungrier and gain weight. Plenty of doctors and podcasters push it, and it sounds logical.

Researchers tested it. In a tightly controlled study at the US National Institutes of Health, people lived in a ward and ate either a high-carb, low-fat diet or a low-carb keto diet, as much as they liked. The theory predicted the keto group would eat less. The opposite happened. The high-carb group ate about 690 fewer calories a day and lost more body fat over those two weeks.

Other controlled studies show the same thing. When protein and calories are matched, low-carb and higher-carb diets give about the same fat loss.

So why does low carb work for some guys?

Because it cuts out a lot of easy calories. Chips, beer, pastries, lollies and takeaway are mostly carbs and fat. Drop them and the calories fall without trying. You also lose some water at the start, which makes the scales drop fast. That’s a real win, it just isn’t magic. If low carb suits you, great. If you love rice, you can still get lean.

When does insulin really matter?

Here’s the part worth knowing. Insulin resistance is when your muscles stop listening to insulin properly. Your body has to pump out more and more to get the job done. It’s common in men with a big belly, poor sleep, a desk job and high stress, and it can lead to type 2 diabetes and heart problems.

The belly fat sitting around your organs, called visceral fat, is closely tied to this. It’s a chicken and egg thing. More belly fat makes insulin work worse, and poor insulin control goes along with more belly fat.

What reliably improves it:

• Losing some fat. Even a few kilos makes a difference.
• Lifting weights. Muscle is your biggest sugar sponge. More muscle, more places for sugar to go.
• Training in general. Muscles that work stay more sensitive to insulin for hours to a day or two afterwards.
• Walking after meals. Even short walks lower the sugar and insulin rise after eating.
• Sleep. Short sleep makes insulin work worse the next day.

Is eating every few hours bad for insulin?

You’ll hear that every snack “spikes” insulin and keeps you storing fat all day. For a healthy person, insulin going up after a meal and coming back down is normal. What matters more is how much you eat in total and how active you are. That said, constant grazing on biscuits and lollies at your desk usually means more calories, so cutting the mindless snacks is still a good move.

What should I actually do?

Use the Stronghold Fuel Rule. It takes the useful bits of the insulin story and drops the hype:

1. Protein first. Eat the protein and veg on your plate before the carbs. In studies, that order gave a smaller sugar and insulin spike after the meal.
2. Earn your carbs. Put most of them in the meal before or after training, when your muscles want them most.
3. Other meals: protein, veg and some healthy fat. These keep you full.
4. Walk it off. A 10 minute walk after your biggest meal.
5. Calories still count. Keep a small gap to lose fat.

What about the doctors who say insulin is everything?

Some researchers, like Dr Ben Bikman, talk a lot about insulin, and they’re right about one big thing: high insulin and insulin resistance are common, under-diagnosed and linked with belly fat and heart risk. Where it gets stretched is the jump from that to “just keep insulin low and the fat falls off”. The controlled studies don’t back that. Calories still run the show for fat loss. Insulin control is a health win you get along the way.

FAQ

Does insulin stop fat burning?

For a few hours after a meal, it slows it. Over a day and a week, total calories decide whether you lose fat.

Should I do keto to lower my insulin?

You can if you enjoy it, but it isn’t required. Fat loss, training and walking improve insulin sensitivity on any sensible diet.

Does apple cider vinegar help with insulin?

A little, for that one meal. A 2017 review of 11 small studies found vinegar taken with a meal lowered that meal’s blood sugar and insulin rise. The effect is small to moderate, the studies were small and varied, and none showed a change to body fat or long-term insulin sensitivity. Take it with a meal that has carbs, because it only affects that meal. Always dilute it, about a tablespoon in a glass of water, and never drink it straight, as it can damage your teeth and throat. If you take diabetes medication or insulin, or it gives you reflux, check with your GP first. Lifting, walking and sleep do far more.

How do I know if I’m insulin resistant?

You can’t tell by feel. Ask your GP for a blood test. A big waist, high blood pressure and a family history of diabetes are good reasons to ask.

Read next

• Do Carbs Make You Fat?
• Testosterone, Hormones and Belly Fat After 40
• Stress and Belly Fat: Is Cortisol Why I Can’t Lose My Gut?
• StrongCEO: a simple plan for busy men

This article is general information only. If you have diabetes or pre-diabetes, take insulin, metformin, weight loss injections or any blood sugar medication, or have a medical condition, see your GP before changing your diet or training. Changing what and when you eat can change how your medication works.