Over-indulging during the holidays and the start of a new year gets a lot of Kiwis thinking about life changes, in particular weight loss.

The reasons so many people, particularly women, feel they need to lose weight are complex, but the bottom line is most will try dieting at some point.

Fad diets fall in and out of favour every year, with some promising drastic weight loss quickly and others promoting lifestyle changes that get results over a longer period.

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Some diets restrict food intake so severely they can be harmful - and the longer weight takes to lose, the more likely it is to stay gone.

The Herald has asked three experts their opinion on eight of the most name-checked diets of 2017 to see what they recommend if you want to try shifting a few kilos.

Here's what they have to say.

Niki Bezzant, food and nutrition writer and editor at large for Healthy Food Guide, said the weight-loss industry thrived on the fact that people couldn't sustain a diet and would go on and off them during their lives.

"If you do anything you've got to say 'can I do this for the rest of my life?'.

"If it's something that's got lists of foods you can have and lists of foods you can't have then it's probably not."

She did not want to comment on specific diets, saying she wished people would focus instead on making their lives more healthy.

"Don't go on a diet, diets don't work. Don't be sucked in," she said.

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"Spend money on beautiful healthy fruit and vegetables, not on a diet book or a 12-week programme."

Saying people should try to gain health rather than lose weight was not "as sexy" as promising you'll lose 2kg in a week - but it was more realistic long term, she said.

"The weight doesn't stay off unless you make a permanent change. So you're better off making small changes and losing the weight slowly."

Intermittent fasting works by severely restricting calorie intake for two days of the week. Photo / Getty
Intermittent fasting works by severely restricting calorie intake for two days of the week. Photo / Getty
There is little research backing up the claim you needed to keep your
There is little research backing up the claim you needed to keep your "ratios" right through food intake. Photo / 123rf

The Zone diet

The Zone diet is a low-carbohydrate diet. The dieter consumes calories from carbohydrates and protein in a specified ratio, eating five times a day to create a sense of satiety that discourages overeating.

Brown:

"It's complicated, probably overly complicated. It's lower calories so you will lose weight on it but it's quite confusing for people and not really necessary."

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There was little research backing up the claim you needed to keep your "ratios" right through food intake.

"The body is actually pretty good at doing that itself."

Some of the principles, such as limiting carbohydrates, was healthy, but the diet took this too far, she said.

Braakhuis: If you went to the effort of calculating all the blocs like the diet instructed you to, then the diet would be a low-calorie, moderate-protein, moderate-carb diet, Braakhuis said.

But many people read the book and followed the principles, which could be interpreted into a way of eating that was high-fat and high-protein and few restrictions. The misunderstanding was easy to make and could be harmful, she said.

A diet high in red meat could cost your wallet - and the earth. Photo / 123rf
A diet high in red meat could cost your wallet - and the earth. Photo / 123rf

Paleo diet

The Paleolithic (Paleo) diet restricts people to eating the kinds of foods available to humans during the Paleolithic era. It is a high-protein diet that excludes several foods including cereal grains (so, bread), dairy and refined sugar.

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Brown:

"On the pro side, it does emphasise whole foods, less-processed foods, which is nice," she said.

"But what it does that we really don't like is it excludes food groups."

Excluding dairy and grains meant excluding good sources of calcium and fibre. It wasn't necessary for weight loss and it wasn't sustainable long-term, Brown said.

A diet high in red meat could cost your wallet - and the earth. Intensive farming for meat uses up huge amounts of land and resources, Brown said.

"If you are worried about global warming then it's probably not the best diet to go on."

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Braakhuis: The main issue is for over-consuming protein and we don't really know what the long-term effects of those are."

Kidney function could be affected and gut health compromised, with a diet high in red meat likely to cause constipation, Braakhuis said.

"As adults we're supposed to use our teeth to chew food" - which is why we don't need baby food. Photo / 123rf

The baby food diet

This fad diet is used for cutting calories and controlling portions. It involves replacing one or two meals a day or snacks with baby food, which comes in small portions and contains few calories.

Brown:

"It's so ridiculous. I've never heard anything so stupid. It's not sustainable, it's for quick weight loss.

"It takes the enjoyment out of food. Having a jar of baby food, I couldn't think of anything worse."

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Braakhuis: "As adults we're supposed to use our teeth to chew food. And our stomach is supposed to churn and … as soon as you take that away, baby food is all mushy.

"It's a bit like muscles - if we don't use them they don't get any fitter," she said.

"It's not a good idea to be on a baby food diet - that just seems silly."

 Those who come from Greece, Spain and Southern Italy tend to use a lot of olive oil. Photo / 123rf
Those who come from Greece, Spain and Southern Italy tend to use a lot of olive oil. Photo / 123rf

Mediterranean diet

More of a lifestyle change than a diet focusing on calorie intake, the Mediterranean diet is based on the traditional eating habits of those who come from Greece, Spain and Southern Italy. It involves eating a lot of vegetables, fruits, lean protein and olive oil.

Brown:

"This is not a fad, this is going back to what some of the poorer countries in the Mediterranean ate which turned out to be quite good.

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"It's full of whole grains and legumes and nuts which are really good. It emphasises the healthy fats, it does emphasise fish which is a good and a bad thing."

The plant-based diet was easy on the environment, though if everyone followed it
overfishing would be a risk, Brown said.

"It really does emphasise eating with the whanau and friends, so really it's a lifestyle thing."

The diet was not tailored toward weight loss, but if people exercised portion control they may lose some weight as a side effect of following the style of eating, Brown said.

Braakhuis: There was a lot of evidence showing this style of eating was good for reducing rates of heart disease, Braakhuis said.

She said a lot of diets restricted people's ability to enjoy food with friends and family - an important social part of life.

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Anyone interested in the Mediterranean diet should see it as a lifestyle change that included eating more socially and being more connected with friends and family at meal times - something that hadn't necessarily translated among those hyping the diet in the west, she said.

Fad diets fall in and out of favour every year. Photo / File
Fad diets fall in and out of favour every year. Photo / File

DASH (Dietary Approaches to Stop Hypertension) diet

Originally formulated to lower blood pressure, the DASH diet is a guide for a balanced diet low in sweet treats. It is more of a lifestyle change and weight loss would require portion control.

Brown:

"'It's an American adaptation, if you like, of the Mediterranean diet."

But it was possibly more forgiving, allowing sweet treats occasionally, she said.

If people exercised portion control, they should lose weight slowly over the long-term as it promoted healthful eating, Brown said.

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"I would recommend that one."

Braakhuis: "The DASH diet seems to come from evidence which looks like it reduces blood pressure, and puts it into a diet.

"The evidence is strong for hypertension and it is probably good for weight loss simply because it advocates for fruit and vegetable intake and lots of it … which if you follow you should probably lose weight."

No one likes cabbage enough to stick to this diet for a long period of time. Photo / 123rf
No one likes cabbage enough to stick to this diet for a long period of time. Photo / 123rf

Cabbage soup diet

Promising quick weight loss, the cabbage soup diet promotes eating large amounts of, you guessed it, cabbage soup - and little else.

Brown:

"That's another stupid one. It's definitely not nutritionally balanced, it's not sustainable."

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People might see dramatic results in the first week or so, but they were very unlikely to keep losing weight or keep the weight off long-term.

"When you lose weight too quickly - more than a kilo a week - you're going to be losing water and stored carbohydrates as well. Some of it will be body fat but not all of it."

Braakhuis: "We can never take one food. It just doesn't happen like that. One food can't do everything.

"There's no way someone can stick to that for a long period time - no one likes cabbage that much."

"When people go into ketosis they don't feel hungry and eat less which is why people think it's a magical state. It's not good for your health long-term." Photo / File

Ketogenic (Keto) diet

The ketogenic diet is a high-fat, high-protein, low-carbohydrate diet that forces the body to burn fats rather than carbohydrates.

Brown:

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Brown compared the ketogenic diet to the Atkins diet and said it could get short-term results, but there was no evidence the weight would stay off.

"People can't stick to these diets for long. What causes us to worry is it does restrict food groups. Your fibre is compromised.

"It's not sustainable long term. People like it because they think 'oh I can have bacon and eggs for breakfast' but if you have bacon and eggs for a month you're kind of over it."

Braakhuis: The ketogenic diet was about making the body go into ketosis - a metabolic state which suppresses your appetite, Braakhuis said.

"When people go into ketosis they don't feel hungry and eat less which is why people think it's a magical state. It's not good for your health long-term."

Eating food should be a social experience. Photo / 123rf
Eating food should be a social experience. Photo / 123rf

The skinny:

Overall, Brown and Braakhuis said diets were less effective - and less enjoyable - than simply making healthy lifestyle choices which included upping exercise.

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"Food is there to be enjoyed, it's very social," Brown said.

"We've got all these diets; if one really worked and it suited everybody, everyone would be on it. The one thing people have to do is adhere to it forever and that's the problem."

If people did want to diet, Brown said, they should try a programme that didn't cut any food groups entirely and which still let them get out and socialise.

"There's no problem having a wine and some chocolate as long as you don't have it every hour of the day."

Braakhuis echoed the fact there was no one solution for everyone.

She said people could take principles they liked from different diets and try them, but said extreme food restriction wasn't the way to go.

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"If anything I'd suggest doing the DASH diet."