Bacon and black coffee for breakfast, or oatmeal and bananas?

If you decided to make a new year’s resolution and try to lose weight in 2019 you are sure to have found a fierce debate online – and among your friends and family – about how best to do it.

It seems as if everyone has an opinion and new fads emerge every year.

Two major studies published in the past year provided more fuel for a particularly polarising topic – the role carbohydrates play in making us fat.

The studies gave scientists some clues, but, like other nutrition studies, they cannot say which diet, if any, is best for everyone.

Veganism: why it’s not just a diet, more a way of life

That is not going to satisfy people who want black-and-white answers, but nutrition research is extremely difficult and even the most respected studies come with big caveats.

People are so different that it is all but impossible to conduct studies that show what really works over long periods.

Before embarking on a weight loss plan for the new year, here is a closer look at some of what was learned last year.

Fewer carbs means less weight?

It is no longer called the Atkins Diet, but the low-carb school of dieting has been enjoying a comeback.

The idea is that the refined carbohydrates in foods such as white bread are quickly converted into sugar in our bodies, leading to energy swings and hunger.

By cutting carbs, the claim is that weight loss will be easier because your body will instead burn fat for fuel while feeling less hungry.

One recent study seems to offer more support for low-carb proponents. But, like many studies, it tried to understand only one sliver of how the body works.

How you can eat a carb-free keto Thanksgiving dinner – and still enjoy it

The study, co-led by an author of books promoting low-carb diets, looked at whether varying carb levels might affect how the body uses energy.

Among 164 participants, it found that those people on low-carb diets burned more total calories than those on high-carb diets.

The study did not say if people lost more weight on a low-carb diet – and did not try to measure that. Meals and snacks were tightly controlled and continually adjusted so everyone’s weight stayed stable.

David Ludwig, a lead author of the paper and researcher at Boston Children’s Hospital, said the study suggests limiting carbs could make it easier for people to keep weight off once they have lost it. He said the approach might work best for those with diabetes or pre-diabetes.

Ludwig said the study was not intended to test long-term health effects or real-world scenarios where people make their own food. The findings also needed to be replicated to be validated, he said.

Caroline Apovian of Boston University’s School of Medicine said the findings were interesting fodder for the scientific community, but that they should not be taken as advice for the average person looking to lose weight.

Do I avoid eating fat to be skinny?

For years people were advised to curb fats, which are found in foods including meat, nuts, eggs, butter and oil. Cutting down on fat was seen as a way to control weight, since a gram of fat has twice as many calories than the same amount of carbs or protein.

Many people say the advice had the opposite effect by inadvertently giving us a licence to gobble up fat-free biscuits, cakes and other foods that were full of the refined carbs and sugars now blamed for our wider waistlines.

Nutrition experts gradually moved away from blanket recommendations to limit fats for weight loss.

Want to go on the keto diet? 9 things you should know before you start

Fats are necessary for absorbing important nutrients and can help us feel full. But that does not mean you have to live on eating steak drizzled in butter to be healthy.

Bruce Y. Lee, a professor of international health at Johns Hopkins University in the US, said the lessons learned from the anti-fat fad should be applied to the anti-carb fad: don’t oversimplify advice.

“There’s a constant look for an easy way out,” Lee said.

So which is better?

Another big study over the past year found low-carb diets and low-fat diets were about equally effective for weight loss. Results varied by individual, but after a year people in both groups shed an average of 12 to 13 pounds (5.4 to 5.9 grams).

The author said the findings do not contradict Ludwig’s low-carb study. Instead, they suggest there may be some flexibility in the ways we can lose weight.

Participants in both groups were encouraged to focus on minimally processed foods such as produce and meat prepared at home. Everyone was advised to limit added sugar and refined flour.

Vegan, organic, non-GMO and gluten-free: chefs are answering the call for dietary needs

“If you got that foundation right, for many, that would be an enormous change,” Christopher Gardner, of Stanford University, who was one of the study’s authors, said.

Limiting processed foods could improve most diets by cutting down overall calories, while still leaving room for people’s preferences.

That is important because for a diet to be effective, a person has to be able to stick to it. A breakfast of fruit and oatmeal may be filling for one person, but leave another person hungry soon after.

Gardner said the study had its limitations, too.

Participants’ diets were not controlled. Instead, people were told how to achieve eating a low-carb or low-fat in regular meetings with dietitians, which may have provided a support network most dieters do not have.

So, what works?

In the short term you can probably lose weight by eating only raw foods, or going vegan, or cutting out gluten, or following another diet plan that catches your eye.

However, what will work for you over the long term is a different question.

Zhaoping Li, director of the clinical nutrition division at the University of California, Los Angeles, said there was no single set of guidelines that helped everyone lose weight – and to keep it off. It’s one reason diets often fail – they do not consider the many factors that drive us to eat what we do.

To help people lose weight, Li looks at their eating and physical activity routines to identify improvements they will be able to live with.

“What sticks is what matters,” Li said.

Want more stories like this? Sign up here. Follow STYLE on Facebook, Instagram and Twitter